Desensitization of Adrenaline-Induced Red Blood Cell H+ Extrusion in Vitro After Chronic Exposure of Rainbow Trout to Moderate Environmental Hypoxia (original) (raw)
Related papers
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.
Respiration physiology, 1990
Changes in plasma catecholamine levels were measured in trout exposed to acute hypoxia, in order to correlate with acid-base disturbances due to activation of the cAMP-dependent Na+/H+ antiporters of red blood cells, as previously described (Fiévet B., Respir. Physiol. 74, 99-114, 1988). The extracellular acidosis corresponding with the stimulation of the exchangers, occurred when arterial oxygen partial pressure (PaO2) reached around 15 Torr (Thomas S., Respir. Physiol. 74, 77-90, 1988). This blood pH drop coincided with a marked increase in plasma catecholamine levels. The catecholamine secretion was transient and the hormones were cleared provided PaO2 remained above 10 Torr. On the other hand, when PaO2 remained below 10 Torr, there was a persistent secretion of catecholamines. This is in agreement with the fact that the exchangers are 'turned off' or sustained when PaO2 remains above or below 10 Torr respectively, as previously described. Following the transient hormone...
Adrenaline effects on the oxygen binding to trout hemoglobin
Comparative Biochemistry and Physiology Part C: Comparative Pharmacology, 1991
l. The functional behaviour of both purified and intracellular trout hemoglobin has been investigated in the presence and absence of adrenaline and at different pHs.
Respiration Physiology, 1989
The concentrations of plasma catecholamines, epinephrine and norepinephrine, were monitored in rainbow trout ($almo gairdner 0 after acute (30 rain) exposure to various levels of extcrna~ hypercapnia (water Pco, (Pwco2) = 0-1 !.3 Tort) under normoxic (water Po2 (Pwo2) = 153 + I.I Ton) or hyperoxic (Pwo,-653 + 27.0 Torr) conditions. Whole blood pH decreased to a similar extent as a function ofexternai carbon dioxide tensions in both the normoxic and hyperoxic hypercapnic groups. Arterial oxygen content, however, declined only during normoxic hyperc~pnia. Similarly, plasma catecholamines (primarily epinephrine) increased only during normoxic hypercapnia in proportion to the severity of the whole blood acidosis. Epinephrine levels were elevated 10-fold from 0.70 + 0.06 nM to 7.06 + 3.7 nM at the highest concentration of external CO, (I 1.3 Tort) whereas norepinephrine increased 3-fold from 0.56 + 0.07 nM to 1.62 ± 0.40 nM. The absence ofcatecholamine release into the circulation during hyperoxic hypercapnia was not due to inhibition of the 'catecholamine-releasing process' by abnormally elevated arterial oxygen tensions (Pao~ = ~ 400 Ton') because acutely anaemic and thus hypoxemic fish (haematocrit = 4.9 + 0.7%) displayed identical elevations of plasma catecholamines under both normoxic and hyperoxic conditions. The results of these experiments demonstrate that a~lerial hypoxemia, rather than blood acidosis per se, is the proximate stimulus causing catecholamine mobilization in rainbow trout during short-term environmental hypercapnia. Acidosis; Blood; CatecholawJnes; Fish; Hypercapnia; Hypoxemia The circulating levels of catecholamines, epinephrine and/or norepinephrine, increase during numerous experimentally-induced stresses in fish including imposed environmental disturbances (e.g. hypoxia, hypercapnia, air-exposure) and after severed types of exercise regimes. The mobilization of catecholamines is thought to be important in compensating the deleterious effects of stress on gas transfer and acid-base balance (see review by Perry and Wood, 1989). In table 1, we have compiled plasma catecholamine
Respiration Physiology, 1989
The involvement of catecholamines in regulating arterial oxygen content (Cao2) during hypercapnic acidosis in rainbow trout (Salmo gairdneri) was investigated by comparing physiological responses during acute normoxic hypercapnia (a condition in which plasma epinephrine is elevated) and acute hyperoxic hypercapnia (a condition in which plasma epinephrine is not elevated). Red blood cell pH (rbc pH) was maintained significantly higher in the normoxic hypercapnic fish despite similar reductions in whole blood pH (pile) in both groups. Elevation of rbc pH in the normoxic hypercapnic fish was abolished by pre-treatment with the p-adrenoceptor antagonist, propranolol, whereas injection of epinephrine into hyperoxic hypercapnic fish significantly raised rbc pH. Arterial blood oxygen carrying capacity increased only in the normoxic hypercapnic fish due to significant increases in blood haemoglobin (Hb) levels. The ability of trout to elevate blood Hb was abolished by pre-treatment with the 0¢.adrenoceptor antagonist, phentolamine. Injections of epinephrine into normocapnic fish caused increases in blood Hb and concomitant decreases in spleen wet weight and Hb content. Adrenergic elevation ofblood Hb was not observed in splenectomized fish. Cao:, although depressed during normoxic hypercapnia, was indeed regulated when compared to Cao2 values predicted from the in vitro Root effect. Pre-treatment with phentolamine, but not propranoloI, abolished the ability of trout to regulate Caor Blood; Catecholamines; tlypercapnia; Oxygen; Red blood cell; Salmo gairdneri; Spleen Whole blood acidosis in teleost fishes may impair oxygen transport due to the effect of H + ions on reducing haemoglobin saturation via the Root effect. It has been suggested (e.g. Perry and Wood, 1989), however, that elevation of plasma catecholamine levels concurrent with acidosis promotes a variety of compensatory responses to minimize depressions of arterial oxygen content. These responses include (a) regulation of red blood cell pH, (b) elevation of arterial oxygen carrying capacity, and (c) increased branchial diffusive and ventilatory conductances. This model has arisen primarily from the results of experiments in which catecholamines were artificially elevated in vivo
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...
Stress and fish, 1981
Austract. A series of experiments was conducted to find out if the swelling of rainbow trout erythrocytes had any influence on the oxygen binding properties of blood. The erythrocytes swelled when the fish were sampled by cardiac puncture, when the fish were subjected to hypoxia at l8°C, and when. in the course of determining the in vivo blood oxygen dissociation curve at 18°C, the ambient 0 2 saturation decreased below 50% for the normoxic fish and below 40% for the hypoxic fish. In hypoxia at 11°C and in the determinations of the in vivo dissociation curves at 8°C the red blood cells did not swell appreciably. The swelling of the erythrocytes leads to a decreased intraerythrocytic ATP concentration. which increases the oxygen affinity of the blood. as indicated by the in vivo oxygen dissociation curves at 18°C. The oxygen affinity increase is probably not caused by a decrease in the formation of ATP-Hb complex, as the ATP/Hb molar ratio did not change, but by an increase in the intraerythrocytic pH. In hypoxia at the low temperatures (8 and 11°C), the oxygen affinity of the blood can be increased by both these mechanisms.
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...