Species differences in the adrenergic responses of fish red cells: studies on whitefish, pikeperch, trout and carp (original) (raw)
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The adrenergic responses of carp (Cyprinus carpio) red cells: effects of PO2 and pH
Journal of Experimental Biology, 1988
Carp (Cyprinus carpio) red cells do not show beta-adrenergic responses when incubated with 10(−5) mol l-1 adrenaline at atmospheric oxygen tension and a pH value close to the in vivo resting pH (approx. 8.1). However, when either the pH or the oxygen tension of the incubation medium is decreased, the adrenergic responses appear, showing that oxygen or an oxygen-linked phenomenon has a direct influence on the response. Once present, the adrenergic red cell response is similar to that of trout: cellular water content, sodium content and intracellular pH all increase. Quantitatively the effect appears to be much smaller in carp than in trout. Adrenaline induces an increase in red cell oxygen content when the oxygen content is plotted as a function of extracellular pH. This effect coincides with the onset of the Root effect and is caused by the adrenaline-induced increase in intracellular pH, since it disappears when the oxygen content is plotted as a function of intracellular pH. The r...
Red blood cells from rainbow trout swell in vitro in an isoosmotic medium upon {jadrenergic stimulation. This response is greater with 5.5 than with 2.5 mM extracellular K.+. The red cells also swell in vivo when the fish are stressed or infused with adrenaline. This in vivo response is blocked by the {j antagonist, propranolol. Simultaneously with the in vitro swelling the intracellular proton concentration decreases and the extracellular level increases: incubation with 5 • 10-' M adrenaline increases intracellular pH by 0.1 units, reflecting a 15% decrease in intraerythrocytic proton concentration. The increase in intracellular pH associated with adrenergic swelling will raise blood oxygen affinity in stress, offsetting detrimental effects of hypoxia and exercise on oxygen loading in the gills.
Journal of Experimental Zoology, 1987
The effects of extracellular pH and beta-adrenergic stimulation on the volume and pH of rainbow trout red cells were studied in HC03-/ C02 buffered media. A decrease in extracellular pH caused an increase in red cell volume and a decrease in intracellular pH. The pH-induced changes in cell volume were inhibited by 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic acid, (DIDS), an inhibitor of the anion exchange pathway, but not by amiloride, an inhibitor of Na+/H+ exchange, indicating that these volume changes are mainly associated with movements of chloride across the red cell membrane, and that the Na+Mf exchanger is not activated by changes in intracellular pH alone. The adrenergic drug, isoproterenol, promoted cell swelling and proton extrusion even in the presence of 10 mM HCOB-, showing that the adrenergic response plays a significant role in the control of cytoplasmic pH. These responses were enhanced by a decrease in extracellular pH, showing that the adrenergic response is of benefit to stressed animals. DIDS markedly enhanced the effect of isoproterenol on the pHi, but abolished the increase in red cell volume. The effects of furosemide were similar to those of DIDS, suggesting that these transport inhibitors have a similar mode of action. Amiloride, on the other hand, inhibited both the volume and the pH changes associated with adrenergic stimulation. These observations support the double Naf/Hf and HC03-/Cl-exchange model of adrenergic swelling in fish red cells.
Aquaculture, 1999
Red blood cells from rainbow trout rely mainly on oxidative phosphorylation to cover the energy demand of processes such as cation transport and protein synthesis. Stimulation of these cells with catecholamines leads to an increase in the intracellular Na q concentration due to adrenergic activation of the erythrocyte Na q -H q exchanger. Adrenergic stimulation also increases red cell oxidative phosphorylation which largely can be ascribed to increased activity of the Na q -K q pump in response to the increase in intracellular Na q concentration. Based on experiments with the Na q -ionophore, monensin, it has been suggested that adrenergic stimulation is a prerequisite for the increase in oxidative ATP-production observed when intracellular Na q is increased. Using washed red blood cells from rainbow trout, the present study examines the role for adrenergic stimulation in the metabolic response when intracellular Na q is elevated. It is Ž y8 y6
The Journal of experimental biology, 1986
A fall in blood pH was generated either by infusion of HCl or by reducing gill ventilation and raising blood PCO2 in rainbow trout, Salmo gairdneri Richardson. The acute acidosis resulting from HCl infusion caused an increase in plasma adrenaline and noradrenaline concentrations, the adrenaline increase being proportional to the decrease in blood pH. Fish subjected to a prolonged respiratory acidosis, caused by a reduction in gill ventilation, showed no increase in catecholamines 24 h after the change in gill ventilation. We suggest that catecholamine levels increase in response to a pH decrease, but if acidotic conditions are maintained, circulating catecholamines return to low levels. There was a much smaller decrease in erythrocytic pH with a fall in plasma pH when catecholamine levels were high. This ameliorating effect of catecholamines on erythrocytic pH during a plasma acidosis maintains the oxygen-carrying capacity of the haemoglobin. If erythrocytic pH was decreased by incr...
Journal of Experimental Biology
We investigated the mechanisms by which adrenergic activation of sodium/proton exchange reduces the pH gradient across the membrane of rainbow trout red cells. In untreated cells, adrenergic stimulation caused a significant increase in the proton distribution ratio ([H+]e/[H+]i) across the red cell membrane. The increase in the proton distribution ratio caused by adrenergic stimulation was inhibited by the protonophore 2,4-dinitrophenol (2,4-DNP). Thus, sodium/proton exchange displaces protons from electrochemical equilibrium. Active regulation of intracellular pH by sodium/proton exchange is possible, because the extracellular dehydration of carbonic acid to carbon dioxide is uncatalyzed. The increase in proton distribution ratio caused by adrenergic stimulation was inhibited in red cell suspensions to which extracellular carbonic anhydrase had been added before stimulation. In contrast, inhibition of intracellular carbonic anhydrase markedly increased the pH changes induced by adr...
The Journal of experimental biology, 1997
The metabolic response of sea bream (Sparus aurata) red blood cells to adrenergic stimulation was determined in normoxia and anoxia. In the presence of oxygen, red blood cells swelled and then recovered their resting volume. Continuous monitoring of oxygen uptake displayed the kinetics of the increase in the oxygen affinity of haemoglobin. Cell volume recovery correlated with an activation of ATP consumption, and the energy equilibrium was restored by increasing the rates of respiration and glycolysis. When the respiratory chain was blocked, adrenergic stimulation increased the rates of ATP consumption and glycolysis of red blood cells. Moreover, adrenergic stimulation of deoxygenated erythrocytes also increased cell volume but did not enhance glycolysis or ATP consumption, and the cells remained swollen. Our results suggest that there is an oxygen-linked signal transducer that activates ATP-consuming processes, provided that the adrenergic stimulation occurs in the presence of oxygen.
Journal of Experimental Biology, 2000
In this study, we examined whether the adrenergic volume response of teleost erythrocytes is related to cell maturity. Rainbow trout (Oncorhynchus mykiss) were made anaemic by reducing their haematocrit to approximately 50 % of the original value. After 3–4 weeks, small, young erythrocytes were seen in the circulation. By measuring the volume distribution of blood samples from anaemic fish before and after noradrenaline stimulation (10 min, 10(−5)mol l(−1) final concentration), we were able to show that the volume response of young, immature erythrocytes to catecholamine stimulation was greater than that of mature erythrocytes. In addition, the membrane fluidity, measured using the steady-state fluorescence polarisation method, was greater in anaemic fish after 24 days of recovery from bleeding than in control fish. Since blood from anaemic fish contained a large fraction of immature erythrocytes, this result indicates that the fluidity of the membrane of immature erythrocytes is gr...
Journal of Experimental Biology, 1999
The transport pathways mediating regulatory volume increase (RVI) and β-adrenergic responses in red cells of the European flounder Platichthys flesus have been investigated. Hypertonic treatment under a low-PO2 atmosphere led to a complete RVI and to a three- to fourfold increase in Na+ influx. The RVI and the activated Na+ influx were blocked by the transport inhibitors amiloride and 4, 4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS), both at a concentration of 10(−4)mol l-1, and the RVI was abolished in a Na+-free saline, indicating the involvement of a hypertonically induced Na+/H+ exchanger and an accompanying Cl-/HCO3- exchanger. Both the hypertonically induced Na+ influx and the RVI were blocked by oxygenation of shrunk cells. The β-adrenergic agonist isoproterenol also strongly activated a Na+ influx and caused cell swelling. This response was also inhibited by amiloride and DIDS but was unaffected by oxygenation. Simultaneous application of isoproterenol and hyperto...