Evaluation of oral administration of cortisol and metyrapone: the effects on serum cortisol in rainbow trout (Salmo gairdneri).

The effect of manipulating dietary levels of cortisol and metyrapone on peripheral concentrations of serum cortisol was examined in rainbow trout, Salmo gairdneri. Fish were fed 0, 10, 20, 30, 40 or 50 mg/kg body weight/day of metyrapone or cortisol for 7 days. All levels of cortisol tested increased peripheral levels of serum cortisol. Feeding a level of 30-40 mg/kg body weight/day of metyrapone depressed serum cortisol. We describe, herein, a noninvasive technique for suppression or stimulation of serum cortisol in rainbow trout.