Loss of capacity to elevate plasma cortisol in rainbow trout (Oncorhynchus mykiss) treated with a single injection of o,p'-dichlorodiphenyldichloroethane.

The organochlorine o,p'- dichlorodiphenyldichloroethane (o,p'-DDD) is a metabolite of dichlorodiphenyltrichloroethane (DDT), known for its adrenolytic actions in birds and mammals. The effects of o,p'-DDD on the cortisol stress response were investigated in rainbow trout, Oncorhynchus mykiss, in a dose-response study in vivo. A dose-dependent decrease in plasma cortisol levels was observed on days 7 and 14 after a single i.p. injection of o,p'-DDD. Treatment with o,p'-DDD had no effect on weight gain, hematocrit, and gonado- or hepatosomatic index but decreased liver glycogen reserves. The results indicate that o,p'-DDD is an adrenotoxic compound in rainbow trout and that its effects can be detected even 14 d postinjection.