|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
Desensitization of Adrenaline-Induced Red Blood Cell H+ Extrusion in Vitro After Chronic Exposure of Rainbow Trout to Moderate Environmental Hypoxia
1 Department of Biology, University of Ottawa, 30 George Glinski, Ottawa, Ontario, Canada; CNRS, Laboratoire de Physiologie Animale, Faculté des Sciences et Techniques, Université de Bretagne Occidentale, 6 Avenue Victor he Gorgeu, F-29287 Brest, France
2 Department of Biology, University of Ottawa, 30 George Glinski, Ottawa, Ontario, Canada
3 Department of Biology, University of Ottawa, 30 George Glinski, Ottawa, Ontario, Canada; Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA
4 Department of Biology, University of Ottawa, 30 George Glinski, Ottawa, Ontario, Canada; Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada
The sensitivity of red blood cell Na+/H+ exchange to exogenous adrenaline was assessed in vitro using blood withdrawn from catheterized rainbow trout (Oncorhynchus mykiss) maintained under normoxic conditions [water PO2, (PwO2)=20.66 kPa] or after exposure to moderate hypoxia (PwO2=6.67-9.33 kPa) for 48 h, which chronically elevated plasma adrenaline, but not noradrenaline, levels. Peak changes in whole-blood extracellular pH over a 30 min period after adding 50–1000 nmoll-1 adrenaline were employed as an index of sensitivity; the blood was pre-equilibrated to simulate arterial blood gas tensions in severely hypoxic fish (PaO2=2.0 kPa, PaCO2=0.31 kPa). Blood pooled from normoxic fish displayed a dose-dependent reduction in whole-blood pH after addition of adrenaline. Blood pooled from three separate groups of hypoxic fish, however, displayed diminished sensitivity to adrenaline, ranging from complete desensitization to a 60%reduction of the response. Subsequent experiments performed on blood from individual (i.e. not pooled) normoxic or hypoxic fish demonstrated an inverse correlation between the intensity of H+ extrusion (induced by exogenous adrenaline addition) and endogenous plasma adrenaline levels at the time of blood withdrawal. However, acute increases in plasma adrenaline levels in vitro did not affect the responsiveness of the red blood cell to subsequent adrenergic stimulation. The intensity of H+ extrusion was inversely related to the PaO2 in vivo between 2.67 and 10.66 kPa, and directly related to the logarithm of the endogenous plasma adrenaline level. The results suggest that desensitization of Na+/H+ exchange in chronically hypoxic fish is related to persistent elevation of levels of this catecholamine. This desensitization can be reversed in vitro as a function of time, but only when blood is maintained under sufficiently aerobic conditions.
Key words: red blood cell, catecholamines, hypoxia, Na+/H+ exchange, Oncorhynchus mykiss
Accepted on October 5, 1990
This article has been cited by other articles:
|
|
 |
|
  K. Lapner, C. Montpetit, and S. Perry Desensitisation of chromaffin cell nicotinic receptors does not impede catecholamine secretion during acute hypoxia in rainbow trout (Oncorhynchus mykiss) J. Exp. Biol., January 5, 2000; 203(10): 1589 - 1597. [Abstract] [PDF]
|
|
|
|
 |
|
 A. K. Gamperl, M. M. Vijayan, C. Pereira, and A. P. Farrell beta -Receptors and stress protein 70 expression in hypoxic myocardium of rainbow trout and chinook salmon Am J Physiol Regulatory Integrative Comp Physiol, February 1, 1998; 274(2): R428 - R436. [Abstract] [Full Text] [PDF]
|
|
