Clearance of corticosteroids in yearling coho salmon, Oncorhynchus kisutch, in fresh water and seawater and after stress.

The metabolic clearance rate of corticosteroids determined after a single injection of [3H]cortisol was higher in fish acclimated to seawater (SW) than in those acclimated to fresh water (FW). Uptake and retention of corticosteroids in liver, gill filaments, and gall bladder bile were greater in SW than in FW fish. The stress of long-term (5 days), but not short-term (12 hr), continuous confinement apparently increased the clearance rate of corticosteroids in both FW and SW fish. Chronic, but not acute, administration of exogenous cortisol, yielding cortisol titers close to the physiological range, appeared to increase the clearance rate of corticosteroids in FW fish.