EFFECT OF ANDROGENS ON DISTRIBUTION AND SECRETION OF CORTISOL IN GONADECTOMIZED MALE SOCKEYE SALMON (ONCORHYNCHUS NERKA)

Gonadectomized male sockeye salmon (Oncorhynchus nerka) were injected twice a week with peanut oil alone or with 2.5 mg of cortisol, 11-ketotestosterone or 17α-methyltestosterone in peanut oil for 4 or 7 weeks. After 7 weeks of treatment, androgen-injected fish had lost most of the red flesh color characteristic of sexually immature salmon, while the skin developed the red color typical of mature and spawned salmon. Changes in body weight were not significant. A single dose of [14C] cortisol was injected intraarterially at the end of the injection period and the clearance of radioactive cortisol was followed in consecutive blood samples taken during a 6-hr interval. The apparent volume of distribution in the inner and outer pools and metabolic clearance rate of cortisol were significantly higher in androgen-treated fish than in controls after 7 weeks of treatment, while half-lives were similar. Cortisol concentrations in plasma during anaesthetic stress were significantly lower in the groups receiving androgens than in control fish. Cortisol secretion rates were significantly higher in 17α-methyltestosterone-treated fish than in control fish both while resting and during anaesthesia. Cortisol injected either for 4 or 7 weeks produced only minor changes in the parameters under study compared to the effects of equal amounts of androgens. © 1969.