The influence of thyroxine and acclimation temperature on glycogen reserves of the frogRana pipiens (original) (raw)
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General and Comparative Endocrinology, 1975
Leopard frogs (Rana pipiens complex) were given daily injections of Na-I-thyroxine (2.0 &lo g body wt) in the dorsal lymph sac, while control animals were given daily injections of equivalent volumes of the alkaline vehicle. Half of the animals were acclimated in darkness at a constant temperature of W, whereas the remaining frogs were acclimated in darkness at 25". At the end of 5.5 days of treatment, the frogs were sacrificed; and oxygen consumption of liver tissue from each animal was measured by differential respirometry at the temperature to which the donor was acclimated. Oxygen consumption of liver tissue from hyperthyroid frogs acclimated at 25" was 21% higher than it was in preparations from control animals acclimated at the same temperature. However, oxygen uptake by liver preparations from hyperthyroid frogs acclimated at 15" did not differ significantly from control levels. Thus, in anuran amphibians-as in reptilian ectotherms-temperature seems to govern the metabolic response of tissues to thyroid hormones.
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 1983
Changes in plasma total thyroxine, triiodothyronine (T3) and metabolic rate were investigated in both hydrated and dehydrated dik-diks after prolonged exposure to ambient temperatures (T a) of 25°C, 35°C and 15°C. AtT a of 25°C, metabolic rate, T3 and T4 were 2.58 W·kg−1, 56.3 ng ml−1 and 0.93 ng ml−1 for the hydrated group, and 1.95 W·kg−1, 70.0 ng ml−1 and 0.85 ng ml−1 for the dehydrated group, respectively. Exposure to 15°C increased metabolic rate and total hormonal concentrations in both groups. Following dehydration and exposure toT a of 35°C a significant decrease in metabolic rate occurred in the presence of a significant increase in both T3 and T4 concentrations. Levels of total plasma T3 and T4 alone are unlikely to be responsible for the decrease in metabolic rate observed in the dehydrated dik-dik antelopes.
General and Comparative Endocrinology, 1990
The specific activities of oxidative enzymes, in response to 3,5,3' triiodo-L-thyronine (T3) and L-thyroxine (T,) administration, were assayed in the teleost, Anabas testudineus pretreated with the beta adrenergic antagonist, propranolol, and the beta islet cell cytotoxin, alloxan. Administration of propranolol or alloxan decreased the activity of cytochrome oxidase, succinate dehydrogenase (SDH), mitochondrial adenosine triphosphatase (Mg2 + ATPase), lactate dehydrogenase (LDH), and cytosolic malate dehydrogenase (cMDH) and did not change that of a-glycerophosphate dehydrogenase (a-GPDH) and glucose-6-phosphate dehydrogenase (G-6-PDH). Propranolol treatment decreased and alloxan administration did not change the mitochondria1 MDH (mMDH) activity. A single injection of T, or T, significantly stimulated cytochrome oxidase and oc-GPDH activities, and decreased Mg2+ ATPase, cMDH, and mMDH activities but did not affect SDH, G-6-PDH, or LDH. The activity of cytochrome oxidase, oc-GPDH, SDH, and Mg2+ ATPase was increased by T, or T3 injection into propranolol or alloxan-treated fish. The data suggest that in teleosts, the stimulatory effect of thyroid hormones on oxidative metabolism is not mediated through the potentiation of adrenaline or insulin action.
Thyroid and hypoxic stress in the newtTriturus carnifex
Journal of Experimental Zoology Part A: Comparative Experimental Biology, 2006
When specimens of the newt Triturus carnifex, under anaesthesia by submersion in a 0.2% chlorbutol solution for 25 min, are isolated in a respiratory chamber at 181C containing water with only 1.3 ppm of oxygen, they consume the oxygen completely in about 3 hr, but they can stay alive for many more hours and wake up with no apparent exterior consequences. Hypoxia induces rapid onset of hepatic steatosis and melanosis, as well as a controlled haemolytic process involving a pool of red blood cells of the same order of size as that held as a reserve in the spleen by animals in an aerial habitat. At the origin of the phenomena is an intense response by the hypophysis, histologically detectable 1 hr from the onset of treatment and confirmed 2 hr later by a highly significant increase in the plasma thyroid-stimulating hormone (TSH) concentration compared with the controls (41.5713.7 mU/L vs. 15.576.2; Po0.005). The thyroid follicles react by reabsorbing their colloid, but instead of an increase in the plasma free T 3 and T 4 concentrations, fT 3 falls significantly (1.570.3 pg/mL vs., the 2.470.7; Po0.05), whereas fT 4 remains stationary (4.070.5 pg/mL vs. 4.670.8; N.S.). After 6 hr, the plasmatic TSH concentration is still higher than in the controls (27.073.0 mU/L vs. 15.576.2; Po0.05), whereas fT 3 and fT 4 remain stable (1.570.3 and 4.470.5 pg/mL, respectively). If T 3 or T 4 labelled with 125 I is administered prior to hypoxia, after 6 hr of treatment the radioactivity is found to be limited exclusively to the liver and kidney; the thyroid, gall bladder and gut result negative, and this does not agree with hypotheses of hormone inactivation by deiodination, sulphation or glucuronidation. This apparently peculiar endocrine path has not been observed in previous studies on hypoxia in vertebrates, because the experiments were always designed to analyse plasma hormone levels after at least 24 hr of hypoxia or during chronic treatments, losing the most interesting phases of the endocrine response. The possibility that the hypoxic newt possesses alternative or complementary metabolic pathways to anaerobic glycolysis to sustain steatogenesis and melanogenesis and maintain the same cardiac activity as the controls is briefly discussed.
Effects of Highly Diluted Sucussed Thyroxine on Metamorphosis of Highland Frogs
These experiments, performed in Graz and in Utrecht, investigate the influence of extremely dilute thyroxine in a special "homeopathic" preparation on two transitions in the metamorphosis of highland amphibia: a) from the 2-legged to the 4-legged stage; b) from the tailed 4-legged stage to the untailed stage, the juvenile frog (performed in the two laboratories in Graz) or to the stage with reduced tail, respectively (performed in Utrecht).
Daily changes in thyroid activity in the frog Rana perezi: Variation with season
Comparative Biochemistry and Physiology Part C: Pharmacology, Toxicology and Endocrinology, 1996
Plasma triiodothyronine (T,) and thyroxine (T4) levels, as well as thyroid free (f) and bound (b) thyroid hormones (TH) content, were determined by radioimmunoassay (RIA) in adult Ranu gereri frogs during a 24 h cycle in winter, spring, summer, and autumn. Significant daily changes in plasma Tj levels were present in all the seasons except for winter, being the lowest values observed during the scotophase. In contrast, plasma T4 only showed significant changes in spring, following a similar pattern to the one described for T3.
Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology, 2018
Oxidative damage is a potential physiological cost of thermoregulation during seasonal adjustments to air temperature (T a) in small mammals. Here, we hypothesized that T a affects serum thyroid hormone levels and these hormones can mediate the changes in metabolic rate and oxidative damage. Mongolian gerbils (Meriones unguiculatus) were acclimated at different T a s (5°C, 23°C and 37°C) for 3 weeks. Serum tri-iodothyronine (T3) levels increased at 5°C but decreased at 37°C compared to the control (23°C). Protein carbonyls increased in liver at 37°C compared with control, however, lipid damage (malonaldehyde, MDA) in both serum and liver was unrelated to T a. After the effects of different T a s on thyroid hormone levels and oxidative damage markers were determined, we further investigate whether thyroid hormones mediated metabolic rate and oxidative damage. Another set of gerbils received 0.0036% L-thyroxin (hyperthyroid), 0.04% Methylimazol (hypothyroid) or water (control). Hypothyroid group showed a 34% reduction in resting metabolic rate (RMR) also 42% and 26% increases in MDA and liver protein carbonyl respectively, whereas hyperthyroid group had higher RMR, liver mass and superoxide dismutase (SOD) compared to control. Serum T3 or T3/T4 levels were correlated positively with RMR, liver mass, and SOD, but negatively with MDA and uncoupling protein 2 (UCP2). We concluded that high T a induced hypothyroidism, decreased RMR and increased oxidative damage, whereas low T a induced hyperthyroidism, increased RMR and unchanged oxidative damage. These data supported our hypothesis that thyroid hormones can be a cue to mediate metabolic rate and different aspects of oxidative and antioxidant activities at different T a s.
Journal of Experimental Zoology, 1993
Insulin stimulation of the glucose uptake by the thyroid gland of the turtle (Chrysemys dorbigni) has been previously reported. The aim of the present study was to examine the influence of different temperatures (6, 25, or 36°C) on this effect. Insulin-stimulated glucose uptake was evident when turtles were acclimated for 15 days at 25" or 36"C, and their glands studied at the respective temperatures. In glands from turtles acclimated at 6"C, this effect was only seen when the preincubation and incubation time was extended from 60 to 300 min. The findings show that in this ectotherm species (1) the insulin effect is temperature dependent, and (2) can be expressed at very low temperature.
Liver glycogen, glucose mobilization and freezing survival in chorus frogs, Pseudacris triseriata
Journal of Thermal Biology, 2005
We compared liver glycogen stores and glucose mobilization during freezing among winters in chorus frogs, Pseudacris triseriata, where populations varied in freezing survival. We also characterized tissue glycogen levels across the annual cycle. Frogs with low liver glycogen stores mobilized low amounts of glucose during freezing, and these were correlated with population variation in freezing survival. Moreover, liver glycogen stores were significantly and positively related to body mass. These data suggest that chorus frogs store liver glycogen in preparation for hibernation and that body size and glycogen stores must reach threshold levels for successful survival of freezing bouts during the winter.