The effects of prolonged epinephrine infusion on the physiology of the rainbow trout, Salmo gairdneri. I. Blood respiratory, acid-base and ionic states.

Rainbow trout were infused continuously for 24 h with epinephrine in order to elevate circulating levels of this hormone to those measured during periods of acute extracellular acidosis (approximately 5 X 10(-8) mol l-1). Concomitant effects on selected blood respiratory acid-base and ionic variables were evaluated. Infusion of epinephrine caused a transient respiratory acidosis as a result of hypoventilation and/or inhibition of red blood cell (RBC) bicarbonate dehydration. The acidosis was regulated by gradual accumulation of plasma bicarbonate. Even though whole blood pH (pHe) was depressed by 0.16 units, RBC pH (pHi) remained constant, thereby causing the transmembrane pH gradient (pHe-pHi) to decrease. A similar effect of epinephrine on RBC pH was observed in vitro, although the response required a higher concentration of epinephrine (2.0 X 10(-7) mol l-1). We speculate that the release of epinephrine during periods of depressed blood pH is important for preventing excessive shifts in RBC pH and for initiating a series of responses leading to plasma HCO3- accumulation and eventual restoration of blood acid-base status.