Desensitization of Adrenaline-Induced Red Blood Cell H+ Extrusion in Vitro After Chronic Exposure of Rainbow Trout to Moderate Environmental Hypoxia (original) (raw)

The sensitivity of red blood cell Na+/H+ exchange to exogenous adrenaline was assessed in vitro using blood withdrawn from catheterized rainbow trout (Oncorhynchus my kiss) maintained under normoxic conditions [water or after exposure to moderate hypoxia for 48 h, which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 nmol l−1 adrenaline were employed as an index of sensitivity; the blood was pre-equilibrated to simulate arterial blood gas tensions in severely hypoxic fish . 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 de...