Matti Vornanen | University of Eastern Finland (original) (raw)
Papers by Matti Vornanen
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, Apr 1, 2007
The Journal of Experimental Biology, Dec 1, 2002
with 200 ms SQ pulses at the same frequencies (664±180 µmol l-1 Ca 2+ , 474±75 µmol l-1 Ca 2+ and... more with 200 ms SQ pulses at the same frequencies (664±180 µmol l-1 Ca 2+ , 474±75 µmol l-1 Ca 2+ and 367±42 µmol l-1 Ca 2+ at 7°C, 14°C and 21°C, respectively). Also, and in contrast to 200 ms SQ pulse stimulation, temperature had little effect on steady-state SR Ca 2+ accumulation during AP stimulation. Furthermore, we observed SR-Ca 2+-dependent inactivation of the L-type Ca 2+ channel current (ICa) at 7°C, 14°C and 21°C, providing additional evidence of maintained SR function in fish hearts over an acute range of temperatures. We conclude that the waveform of the AP may be critical in ensuring adequate SR Ca 2+ cycling during temperature change in rainbow trout in vivo.
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, Apr 1, 2017
Survival of prolonged anoxia requires a balance between cellular ATP demand and anaerobic ATP sup... more Survival of prolonged anoxia requires a balance between cellular ATP demand and anaerobic ATP supply from glycolysis, especially in critical tissues such as the brain. To add insight into the ATP demand of the brain of the anoxia-tolerant red-eared slider turtle (Trachemys scripta) during prolonged periods of anoxic submergence, we quantified and compared the number of Na +-K +-ATPase units and their molecular activity in brain tissue from turtles acclimated to either 21°C or 5°C and exposed to either normoxia or anoxia (6 h 21°C; 14 days at 5°C). Na +-K +-ATPase activity and density per g tissue were similar at 21°C and 5°C in normoxic turtles. Likewise, anoxia exposure at 21°C did not induce any change in Na +-K +-ATPase activity or density. In contrast, prolonged anoxia at 5°C significantly reduced Na +-K +-ATPase activity by 55%, which was largely driven by a 50% reduction of the number of Na +-K +-ATPase units without a change in the activity of existing Na +-K +-ATPase pumps or α-subunit composition. These findings are consistent with the "channel arrest" hypothesis to reduce turtle brain Na +-K +-ATPase activity during prolonged, but not short-term anoxia, a change that likely helps them overwinter under low temperature, anoxic conditions.
Environmental Toxicology and Chemistry, 2019
This is a self-archived version of an original article. This version may differ from the original... more This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details.
Journal of Thermal Biology
Acclimation of ectothermic vertebrates to winter dormancy is associated with reduced energy consu... more Acclimation of ectothermic vertebrates to winter dormancy is associated with reduced energy consumption. In principle, this may be achieved by reducing movement activity, depression of basal cellular functions or by switching from aerobic to anaerobic energy production. To this end, we determined standard (SMR), routine (RMR) and anoxic (AMR) metabolic rates is summer- (SumA) and winter-acclimatized (WinA) crucian carp (Carassius carassius), an anoxia-tolerant teleost fish. RMR was about 40% lower in WinA than SumA fish (p < 0.05), indicating reduced movement in winter. SMR, measured for the first time in crucian carp, was about 45% lower (p < 0.05) in WinA than SumA fish, indicating significant reduction of energy consumption in vital cellular processes. At 2°C, the anoxic metabolic depression, measured from ethanol production, was 78% from the aerobic level at the same temperature. In anoxia-tolerant crucian carp, winter dormancy is achieved in 3 different steps: (1) seasona...
Journal of Experimental Biology, 2021
Heat tolerance of heart rate in fish is suggested to be limited by impaired electrical excitation... more Heat tolerance of heart rate in fish is suggested to be limited by impaired electrical excitation of the ventricle due to the antagonistic effects of high temperature on Na+ (INa) and K+ (IK1) ion currents (INa is depressed at high temperatures while IK1 is resistant to them). To examine the role of Na+ channel proteins in heat tolerance of INa, we compared temperature dependencies of zebrafish (Danio rerio, warm-dwelling subtropical species) and rainbow trout (Oncorhynchus mykiss, cold-active temperate species) ventricular INa, and INa generated by the cloned zebrafish and rainbow trout NaV1.4 and NaV1.5 Na+ channels in human embryonic kidney (HEK) cells. Whole-cell patch-clamp recordings showed that zebrafish ventricular INa has better heat tolerance and slower inactivation kinetics than rainbow trout ventricular INa. In contrast, heat tolerance and inactivation kinetics of zebrafish and rainbow trout NaV1.4 channels are similar when expressed in the identical cellular environment...
Journal of Experimental Biology, 2020
A mechanistic explanation for the tolerance limits of animals at high temperatures is still missi... more A mechanistic explanation for the tolerance limits of animals at high temperatures is still missing, but one potential target for thermal failure is the electrical signaling off cells and tissues. With this in mind, here I review the effects of high temperature on the electrical excitability of heart, muscle and nerves, and refine a hypothesis regarding high temperature-induced failure of electrical excitation and signal transfer [the temperature-dependent deterioration of electrical excitability (TDEE) hypothesis]. A central tenet of the hypothesis is temperature-dependent mismatch between the depolarizing ion current (i.e. source) of the signaling cell and the repolarizing ion current (i.e. sink) of the receiving cell, which prevents the generation of action potentials (APs) in the latter. A source–sink mismatch can develop in heart, muscles and nerves at high temperatures owing to opposite effects of temperature on source and sink currents. AP propagation is more likely to fail a...
Temperature acclimation modifies sinoatrial pacemaker mechanism of the rainbow trout heart by
Recent Advances in Zebrafish Researches, 2018
There are several similarities and differences in electrical excitability between zebrafish and h... more There are several similarities and differences in electrical excitability between zebrafish and human ventricles. Major ion currents generating ventricular action potentials are largely the same in human and zebrafish hearts with some exceptions. A large T-type calcium current is unique to the zebrafish ventricle (absent in human ventricle), and two potassium currents (I Ks and I to) may be absent in zebrafish ventricular myocytes. However, there are substantial differences among alpha subunit isoforms of the ion channel families or subfamilies (e.g. zebrafish Kv11.2 vs. human Kv11.1; zebrafish Kir2.4 vs. human Kir2.1) between human and zebrafish hearts. Contraction of zebrafish ventricle is strongly dependent on extracellular calcium, while human ventricle relies heavily on calcium stores of the sarcoplasmic reticulum. These differences may affect the use of zebrafish as a model in drug screening and safety pharmacology.
Progress in Biophysics and Molecular Biology, 2018
Cardiac voltage-gated sodium channel expression and electrophysiological characterization of the ... more Cardiac voltage-gated sodium channel expression and electrophysiological characterization of the sodium current in the zebrafish (Danio rerio) ventricle
The Journal of experimental biology, 2016
Environmental temperature has pervasive effects on the rate of life processes in ectothermic anim... more Environmental temperature has pervasive effects on the rate of life processes in ectothermic animals. Animal performance is affected by temperature, but there are finite thermal limits for vital body functions, including contraction of the heart. This Review discusses the electrical excitation that initiates and controls the rate and rhythm of fish cardiac contraction and is therefore a central factor in the temperature-dependent modulation of fish cardiac function. The control of cardiac electrical excitability should be sensitive enough to respond to temperature changes but simultaneously robust enough to protect against cardiac arrhythmia; therefore, the thermal resilience and plasticity of electrical excitation are physiological qualities that may affect the ability of fishes to adjust to climate change. Acute changes in temperature alter the frequency of the heartbeat and the duration of atrial and ventricular action potentials (APs). Prolonged exposure to new thermal condition...
Annales Zoologici Fennici, 2013
We compared smolt physiology of Atlantic salmon stocks, that migrate from freshwater stream envir... more We compared smolt physiology of Atlantic salmon stocks, that migrate from freshwater stream environments to a freshwater lake (Lake Saimaa, Finland), from the Neva River (Russia) to the brackish water of the Baltic Sea, and from the Teno River (Finland/ Norway) to the full-strength seawater of the Arctic Ocean. The three fish stocks were reared under common garden conditions, and ion homeostasis, seawater tolerance, activities of gill and kidney Na,K-ATPase and [ 3 H]ouabain binding of gill and kidney tissues were determined at different phases of smoltification. Activity of gill Na,K-ATPase and number of gill [ 3 H]ouabain binding sites reached peak values in May and were strongly suppressed in July. Osmolality and Na + , Cl-, and Mg 2+ ion concentrations of blood plasma decreased during smoltification. α1a and α1b isoforms of gill Na,K-ATPase decreased and increased, respectively, during smoltification. Although small differences appeared at some points in time, the seasonal pattern and magnitude of changes in smolt characteristics were generally similar in the Saimaa salmon and in the anadromous stocks of the Neva and Teno salmon. It is suggested that the strong smoltification process of the landlocked Saimaa salmon is somehow necessary for migration of the young salmon from river to lake and therefore has been retained in evolution.
Annales Zoologici Fennici, 2013
We examined whether gene expression in the young salmon (Salmo salar) gill differs in relation to... more We examined whether gene expression in the young salmon (Salmo salar) gill differs in relation to the salinity of their migration habitat by comparing three salmon stocks: (1) fish that migrate from a river system to Lake Saimaa, (2) fish that migrate to the brackish waters of the Baltic Sea, and (3) fish that migrate to the full-strength salinity of the Arctic Ocean. Transcripts of the gill tissue were measured at three successive developmental stages (parr, smolt and postsmolt) using the cDNA microarray in fish reared under common conditions. The changes in gene expression were qualitatively and quantitatively similar in the three stocks irrespective of the salinity of the natural growing habitat. This suggests that the parr-smolt transformation in the gill tissue of the landlocked freshwater salmon stock is similar to the seawater migrating salmon. The transformation of the gill to a hypoosmotic organ in the freshwater salmon has been retained in evolution, possibly due to its adaptive role as a signal for migration from a relatively poor-growth environment of the river to a more productive lake habitat.
Journal of Experimental Biology, 2018
Calcium (Ca) channels are necessary for cardiac excitation-contraction (e-c) coupling, but Ca cha... more Calcium (Ca) channels are necessary for cardiac excitation-contraction (e-c) coupling, but Ca channel composition of fish hearts is still largely unknown. To this end, we determined transcript expression of Ca channels in the heart of zebrafish (Danio rerio), a popular model species. Altogether 18 Ca channel α-subunit genes were expressed in both atrium and ventricle. Transcripts for 7 L-type (Cav1.1a, Cav1.1b, Cav1.2, Cav1.3a, Cav1.3b, Cav1.4a, Cav1.4b), 5 T-type (Cav3.1, Cav3.2a, Cav3.2b, Cav3.3a, Cav3.3b) and 6 P/Q-, N- and R-type Ca channels (Cav2.1a, Cav2.1b, Cav2.2a, Cav2.2b, Cav2.3a, Cav2.3b) were expressed. In the ventricle, T-type channels formed 54.9%, L-type channels 41.1% and P/Q-, N- and R-type Ca channels 4.0% of the Ca channel transcripts. In the atrium, the relative expression of T-type and L-type Ca channel transcripts was 64.1% and 33.8%, respectively (others accounted for 2.1%). Thus, at the transcript level T-type Ca channels are prevalent in zebrafish atrium and...
Acta Physiologica Scandinavica, 1983
Single ventricular myocytes were isolated by enzymatic dissociation from the rat heart. The myocy... more Single ventricular myocytes were isolated by enzymatic dissociation from the rat heart. The myocytes showed two types of spontaneous contractions: action potential dependent 'electric' contractions which occurred as short bursts, and slowly propagating contraction waves, i.e. phasic contractions. Electric contractions were normally found only in some of the myocytes, but in about 85% of the cells these could be induced by isoprenaline (ISO), phenylephrine (PHE), dibutyryl-cAMP (DB-cAMP) or acetylcholine (ACh). The inducing potency of the drugs was ACh greater than PHE greater than ISO greater than DB-cAMP. When electric contractions were blocked with verapamil, the frequency of phasic contractions was increased by ISO and DB-cAMP, whereas PHE and ACh had not this effect. In 45 min, ISO increased the frequency tenfold. High concentrations (10(-4) and 10(-5) M) of ISO lead to steady contracture of the myocytes in about 40% of the cells. The effect of DB-cAMP was weaker being only about 20% of that of ISO and it never caused steady contractures. The results suggest that alpha receptor activation by PHE does not affect the intracellular calcium movements but that ISO through beta receptor activation and DB-cAMP directly may increase the rate of calcium accumulation by sarcoplasmic reticulum (SR).
The Journal of experimental biology, 2000
Rainbow trout, Oncorhynchus mykiss, inhabit eurythermal environments and must therefore be able t... more Rainbow trout, Oncorhynchus mykiss, inhabit eurythermal environments and must therefore be able to cope with changes in environmental temperature. As ectotherms, their heart is required to maintain cardiac function over a range of ambient water temperatures. This raises important questions concerning the temperature-dependence of cardiac ion channel function in fish hearts, in particular, the channels involved in Ca(2+) transport. Thus, we studied the effects of acute, physiologically relevant temperature changes on the density and kinetics of the L-type Ca(2+) channel current (I(Ca)) in rainbow trout atrial myocytes using the whole-cell patch-clamp technique. Myocytes from fish acclimated to 14 degrees C were first tested at 14 degrees C, then at 21 degrees C and finally at 7 degrees C. Using a square-pulse voltage-clamp in the first series of experiments, the peak density of I(Ca) increased (Q(10)=1.9) as temperature was increased from 14 to 21 degrees C and decreased (Q(10)=2.1) ...
Pflügers Archiv - European Journal of Physiology
Zebrafish are increasingly used as a model for human cardiac electrophysiology, arrhythmias, and ... more Zebrafish are increasingly used as a model for human cardiac electrophysiology, arrhythmias, and drug screening. However, K+ ion channels of the zebrafish heart, which determine the rate of repolarization and duration of cardiac action potential (AP) are still incompletely known and characterized. Here, we provide the first evidence for the presence of the slow component of the delayed rectifier K+channels in the zebrafish heart and characterize electrophysiological properties of the slow component of the delayed rectifier K+current, IKs. Zebrafish atrium and ventricle showed strong transcript expression of the kcnq1 gene, which encodes the Kv7.1 α-subunit of the slow delayed rectifier K+ channel. In contrast, the kcne1 gene, encoding the MinK β-subunit of the delayed rectifier, was expressed at 21 and 17 times lower level in ventricle and atrium, respectively, in comparison to the kcnq1. IKs was observed in 62% of ventricular myocytes with mean (± SEM) density of 1.23 ± 0.37 pA/pF at + 30 mV. Activation rate of IKs was 38% faster (τ50 = 1248 ± 215 ms) than kcnq1:kcne1 channels (1725 ± 792 ms) expressed in 3:1 ratio in Chinese hamster ovary cells. Microelectrode experiments demonstrated the functional relevance of IKs in the zebrafish heart, since 100 μM chromanol 293B produced a significant prolongation of AP in zebrafish ventricle. We conclude that AP repolarization in zebrafish ventricle is contributed by IKs, which is mainly generated by homotetrameric Kv7.1 channels not coupled to MinK ancillary β-subunits. This is a clear difference to the human heart, where MinK is an essential component of the slow delayed rectifier K+channel.
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, Apr 1, 2007
The Journal of Experimental Biology, Dec 1, 2002
with 200 ms SQ pulses at the same frequencies (664±180 µmol l-1 Ca 2+ , 474±75 µmol l-1 Ca 2+ and... more with 200 ms SQ pulses at the same frequencies (664±180 µmol l-1 Ca 2+ , 474±75 µmol l-1 Ca 2+ and 367±42 µmol l-1 Ca 2+ at 7°C, 14°C and 21°C, respectively). Also, and in contrast to 200 ms SQ pulse stimulation, temperature had little effect on steady-state SR Ca 2+ accumulation during AP stimulation. Furthermore, we observed SR-Ca 2+-dependent inactivation of the L-type Ca 2+ channel current (ICa) at 7°C, 14°C and 21°C, providing additional evidence of maintained SR function in fish hearts over an acute range of temperatures. We conclude that the waveform of the AP may be critical in ensuring adequate SR Ca 2+ cycling during temperature change in rainbow trout in vivo.
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, Apr 1, 2017
Survival of prolonged anoxia requires a balance between cellular ATP demand and anaerobic ATP sup... more Survival of prolonged anoxia requires a balance between cellular ATP demand and anaerobic ATP supply from glycolysis, especially in critical tissues such as the brain. To add insight into the ATP demand of the brain of the anoxia-tolerant red-eared slider turtle (Trachemys scripta) during prolonged periods of anoxic submergence, we quantified and compared the number of Na +-K +-ATPase units and their molecular activity in brain tissue from turtles acclimated to either 21°C or 5°C and exposed to either normoxia or anoxia (6 h 21°C; 14 days at 5°C). Na +-K +-ATPase activity and density per g tissue were similar at 21°C and 5°C in normoxic turtles. Likewise, anoxia exposure at 21°C did not induce any change in Na +-K +-ATPase activity or density. In contrast, prolonged anoxia at 5°C significantly reduced Na +-K +-ATPase activity by 55%, which was largely driven by a 50% reduction of the number of Na +-K +-ATPase units without a change in the activity of existing Na +-K +-ATPase pumps or α-subunit composition. These findings are consistent with the "channel arrest" hypothesis to reduce turtle brain Na +-K +-ATPase activity during prolonged, but not short-term anoxia, a change that likely helps them overwinter under low temperature, anoxic conditions.
Environmental Toxicology and Chemistry, 2019
This is a self-archived version of an original article. This version may differ from the original... more This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details.
Journal of Thermal Biology
Acclimation of ectothermic vertebrates to winter dormancy is associated with reduced energy consu... more Acclimation of ectothermic vertebrates to winter dormancy is associated with reduced energy consumption. In principle, this may be achieved by reducing movement activity, depression of basal cellular functions or by switching from aerobic to anaerobic energy production. To this end, we determined standard (SMR), routine (RMR) and anoxic (AMR) metabolic rates is summer- (SumA) and winter-acclimatized (WinA) crucian carp (Carassius carassius), an anoxia-tolerant teleost fish. RMR was about 40% lower in WinA than SumA fish (p < 0.05), indicating reduced movement in winter. SMR, measured for the first time in crucian carp, was about 45% lower (p < 0.05) in WinA than SumA fish, indicating significant reduction of energy consumption in vital cellular processes. At 2°C, the anoxic metabolic depression, measured from ethanol production, was 78% from the aerobic level at the same temperature. In anoxia-tolerant crucian carp, winter dormancy is achieved in 3 different steps: (1) seasona...
Journal of Experimental Biology, 2021
Heat tolerance of heart rate in fish is suggested to be limited by impaired electrical excitation... more Heat tolerance of heart rate in fish is suggested to be limited by impaired electrical excitation of the ventricle due to the antagonistic effects of high temperature on Na+ (INa) and K+ (IK1) ion currents (INa is depressed at high temperatures while IK1 is resistant to them). To examine the role of Na+ channel proteins in heat tolerance of INa, we compared temperature dependencies of zebrafish (Danio rerio, warm-dwelling subtropical species) and rainbow trout (Oncorhynchus mykiss, cold-active temperate species) ventricular INa, and INa generated by the cloned zebrafish and rainbow trout NaV1.4 and NaV1.5 Na+ channels in human embryonic kidney (HEK) cells. Whole-cell patch-clamp recordings showed that zebrafish ventricular INa has better heat tolerance and slower inactivation kinetics than rainbow trout ventricular INa. In contrast, heat tolerance and inactivation kinetics of zebrafish and rainbow trout NaV1.4 channels are similar when expressed in the identical cellular environment...
Journal of Experimental Biology, 2020
A mechanistic explanation for the tolerance limits of animals at high temperatures is still missi... more A mechanistic explanation for the tolerance limits of animals at high temperatures is still missing, but one potential target for thermal failure is the electrical signaling off cells and tissues. With this in mind, here I review the effects of high temperature on the electrical excitability of heart, muscle and nerves, and refine a hypothesis regarding high temperature-induced failure of electrical excitation and signal transfer [the temperature-dependent deterioration of electrical excitability (TDEE) hypothesis]. A central tenet of the hypothesis is temperature-dependent mismatch between the depolarizing ion current (i.e. source) of the signaling cell and the repolarizing ion current (i.e. sink) of the receiving cell, which prevents the generation of action potentials (APs) in the latter. A source–sink mismatch can develop in heart, muscles and nerves at high temperatures owing to opposite effects of temperature on source and sink currents. AP propagation is more likely to fail a...
Temperature acclimation modifies sinoatrial pacemaker mechanism of the rainbow trout heart by
Recent Advances in Zebrafish Researches, 2018
There are several similarities and differences in electrical excitability between zebrafish and h... more There are several similarities and differences in electrical excitability between zebrafish and human ventricles. Major ion currents generating ventricular action potentials are largely the same in human and zebrafish hearts with some exceptions. A large T-type calcium current is unique to the zebrafish ventricle (absent in human ventricle), and two potassium currents (I Ks and I to) may be absent in zebrafish ventricular myocytes. However, there are substantial differences among alpha subunit isoforms of the ion channel families or subfamilies (e.g. zebrafish Kv11.2 vs. human Kv11.1; zebrafish Kir2.4 vs. human Kir2.1) between human and zebrafish hearts. Contraction of zebrafish ventricle is strongly dependent on extracellular calcium, while human ventricle relies heavily on calcium stores of the sarcoplasmic reticulum. These differences may affect the use of zebrafish as a model in drug screening and safety pharmacology.
Progress in Biophysics and Molecular Biology, 2018
Cardiac voltage-gated sodium channel expression and electrophysiological characterization of the ... more Cardiac voltage-gated sodium channel expression and electrophysiological characterization of the sodium current in the zebrafish (Danio rerio) ventricle
The Journal of experimental biology, 2016
Environmental temperature has pervasive effects on the rate of life processes in ectothermic anim... more Environmental temperature has pervasive effects on the rate of life processes in ectothermic animals. Animal performance is affected by temperature, but there are finite thermal limits for vital body functions, including contraction of the heart. This Review discusses the electrical excitation that initiates and controls the rate and rhythm of fish cardiac contraction and is therefore a central factor in the temperature-dependent modulation of fish cardiac function. The control of cardiac electrical excitability should be sensitive enough to respond to temperature changes but simultaneously robust enough to protect against cardiac arrhythmia; therefore, the thermal resilience and plasticity of electrical excitation are physiological qualities that may affect the ability of fishes to adjust to climate change. Acute changes in temperature alter the frequency of the heartbeat and the duration of atrial and ventricular action potentials (APs). Prolonged exposure to new thermal condition...
Annales Zoologici Fennici, 2013
We compared smolt physiology of Atlantic salmon stocks, that migrate from freshwater stream envir... more We compared smolt physiology of Atlantic salmon stocks, that migrate from freshwater stream environments to a freshwater lake (Lake Saimaa, Finland), from the Neva River (Russia) to the brackish water of the Baltic Sea, and from the Teno River (Finland/ Norway) to the full-strength seawater of the Arctic Ocean. The three fish stocks were reared under common garden conditions, and ion homeostasis, seawater tolerance, activities of gill and kidney Na,K-ATPase and [ 3 H]ouabain binding of gill and kidney tissues were determined at different phases of smoltification. Activity of gill Na,K-ATPase and number of gill [ 3 H]ouabain binding sites reached peak values in May and were strongly suppressed in July. Osmolality and Na + , Cl-, and Mg 2+ ion concentrations of blood plasma decreased during smoltification. α1a and α1b isoforms of gill Na,K-ATPase decreased and increased, respectively, during smoltification. Although small differences appeared at some points in time, the seasonal pattern and magnitude of changes in smolt characteristics were generally similar in the Saimaa salmon and in the anadromous stocks of the Neva and Teno salmon. It is suggested that the strong smoltification process of the landlocked Saimaa salmon is somehow necessary for migration of the young salmon from river to lake and therefore has been retained in evolution.
Annales Zoologici Fennici, 2013
We examined whether gene expression in the young salmon (Salmo salar) gill differs in relation to... more We examined whether gene expression in the young salmon (Salmo salar) gill differs in relation to the salinity of their migration habitat by comparing three salmon stocks: (1) fish that migrate from a river system to Lake Saimaa, (2) fish that migrate to the brackish waters of the Baltic Sea, and (3) fish that migrate to the full-strength salinity of the Arctic Ocean. Transcripts of the gill tissue were measured at three successive developmental stages (parr, smolt and postsmolt) using the cDNA microarray in fish reared under common conditions. The changes in gene expression were qualitatively and quantitatively similar in the three stocks irrespective of the salinity of the natural growing habitat. This suggests that the parr-smolt transformation in the gill tissue of the landlocked freshwater salmon stock is similar to the seawater migrating salmon. The transformation of the gill to a hypoosmotic organ in the freshwater salmon has been retained in evolution, possibly due to its adaptive role as a signal for migration from a relatively poor-growth environment of the river to a more productive lake habitat.
Journal of Experimental Biology, 2018
Calcium (Ca) channels are necessary for cardiac excitation-contraction (e-c) coupling, but Ca cha... more Calcium (Ca) channels are necessary for cardiac excitation-contraction (e-c) coupling, but Ca channel composition of fish hearts is still largely unknown. To this end, we determined transcript expression of Ca channels in the heart of zebrafish (Danio rerio), a popular model species. Altogether 18 Ca channel α-subunit genes were expressed in both atrium and ventricle. Transcripts for 7 L-type (Cav1.1a, Cav1.1b, Cav1.2, Cav1.3a, Cav1.3b, Cav1.4a, Cav1.4b), 5 T-type (Cav3.1, Cav3.2a, Cav3.2b, Cav3.3a, Cav3.3b) and 6 P/Q-, N- and R-type Ca channels (Cav2.1a, Cav2.1b, Cav2.2a, Cav2.2b, Cav2.3a, Cav2.3b) were expressed. In the ventricle, T-type channels formed 54.9%, L-type channels 41.1% and P/Q-, N- and R-type Ca channels 4.0% of the Ca channel transcripts. In the atrium, the relative expression of T-type and L-type Ca channel transcripts was 64.1% and 33.8%, respectively (others accounted for 2.1%). Thus, at the transcript level T-type Ca channels are prevalent in zebrafish atrium and...
Acta Physiologica Scandinavica, 1983
Single ventricular myocytes were isolated by enzymatic dissociation from the rat heart. The myocy... more Single ventricular myocytes were isolated by enzymatic dissociation from the rat heart. The myocytes showed two types of spontaneous contractions: action potential dependent 'electric' contractions which occurred as short bursts, and slowly propagating contraction waves, i.e. phasic contractions. Electric contractions were normally found only in some of the myocytes, but in about 85% of the cells these could be induced by isoprenaline (ISO), phenylephrine (PHE), dibutyryl-cAMP (DB-cAMP) or acetylcholine (ACh). The inducing potency of the drugs was ACh greater than PHE greater than ISO greater than DB-cAMP. When electric contractions were blocked with verapamil, the frequency of phasic contractions was increased by ISO and DB-cAMP, whereas PHE and ACh had not this effect. In 45 min, ISO increased the frequency tenfold. High concentrations (10(-4) and 10(-5) M) of ISO lead to steady contracture of the myocytes in about 40% of the cells. The effect of DB-cAMP was weaker being only about 20% of that of ISO and it never caused steady contractures. The results suggest that alpha receptor activation by PHE does not affect the intracellular calcium movements but that ISO through beta receptor activation and DB-cAMP directly may increase the rate of calcium accumulation by sarcoplasmic reticulum (SR).
The Journal of experimental biology, 2000
Rainbow trout, Oncorhynchus mykiss, inhabit eurythermal environments and must therefore be able t... more Rainbow trout, Oncorhynchus mykiss, inhabit eurythermal environments and must therefore be able to cope with changes in environmental temperature. As ectotherms, their heart is required to maintain cardiac function over a range of ambient water temperatures. This raises important questions concerning the temperature-dependence of cardiac ion channel function in fish hearts, in particular, the channels involved in Ca(2+) transport. Thus, we studied the effects of acute, physiologically relevant temperature changes on the density and kinetics of the L-type Ca(2+) channel current (I(Ca)) in rainbow trout atrial myocytes using the whole-cell patch-clamp technique. Myocytes from fish acclimated to 14 degrees C were first tested at 14 degrees C, then at 21 degrees C and finally at 7 degrees C. Using a square-pulse voltage-clamp in the first series of experiments, the peak density of I(Ca) increased (Q(10)=1.9) as temperature was increased from 14 to 21 degrees C and decreased (Q(10)=2.1) ...
Pflügers Archiv - European Journal of Physiology
Zebrafish are increasingly used as a model for human cardiac electrophysiology, arrhythmias, and ... more Zebrafish are increasingly used as a model for human cardiac electrophysiology, arrhythmias, and drug screening. However, K+ ion channels of the zebrafish heart, which determine the rate of repolarization and duration of cardiac action potential (AP) are still incompletely known and characterized. Here, we provide the first evidence for the presence of the slow component of the delayed rectifier K+channels in the zebrafish heart and characterize electrophysiological properties of the slow component of the delayed rectifier K+current, IKs. Zebrafish atrium and ventricle showed strong transcript expression of the kcnq1 gene, which encodes the Kv7.1 α-subunit of the slow delayed rectifier K+ channel. In contrast, the kcne1 gene, encoding the MinK β-subunit of the delayed rectifier, was expressed at 21 and 17 times lower level in ventricle and atrium, respectively, in comparison to the kcnq1. IKs was observed in 62% of ventricular myocytes with mean (± SEM) density of 1.23 ± 0.37 pA/pF at + 30 mV. Activation rate of IKs was 38% faster (τ50 = 1248 ± 215 ms) than kcnq1:kcne1 channels (1725 ± 792 ms) expressed in 3:1 ratio in Chinese hamster ovary cells. Microelectrode experiments demonstrated the functional relevance of IKs in the zebrafish heart, since 100 μM chromanol 293B produced a significant prolongation of AP in zebrafish ventricle. We conclude that AP repolarization in zebrafish ventricle is contributed by IKs, which is mainly generated by homotetrameric Kv7.1 channels not coupled to MinK ancillary β-subunits. This is a clear difference to the human heart, where MinK is an essential component of the slow delayed rectifier K+channel.