AJP - Regulatory, Integrative and Comparative Physiology, Vol 248, Issue 6 651-R659, Copyright © 1985 by American Physiological Society
Cortisol dynamics during seawater adaptation of Atlantic salmon Salmo salar
D. J. Nichols and M. Weisbart
We examined plasma cortisol concentration (PCC), cortisol metabolism, and
cortisol protein binding (CPB) in chronically cannulated Atlantic salmon
(Salmo salar) during seawater (SW) adaptation. PCC rose significantly 2 h
after freshwater (FW) to SW changeover but tended to be lower for 6 days
thereafter. Plasma chloride concentrations began to stabilize 24-48 h after
entry to SW. Cortisol metabolic clearance rate (MCR) was significantly
higher 24 h after SW transfer than in FW; CPB and plasma protein
concentration were significantly lower, but cortisol production rate was
unchanged. The change in plasma chloride after 24 h in SW was negatively
correlated with the change in plasma protein (r = -0.915, n = 9, P less
than 0.001). The changes in CPB and plasma protein were correlated with the
change in MCR (r = -0.643, n = 14, P less than 0.02; r = -0.850, n = 9, P
less than 0.005). We hypothesize that these changes in protein
concentration reflect an ion-induced expansion of extracellular volume and
lead to increased MCR.
