In vitro response to ACTH of the interrenal tissue of rainbow trout (Oncorhynchus mykiss) exposed to cadmium

Plasma cortisol levels and responsiveness of the interrenal tissue to ACTH were determined in rainbow trout (Oncorhynchus mykiss) subjected to acute and subchronic exposures of cadmium (Cd) in the water. Plasma cortisol levels were significantly increased after 2 days of exposure to 1 mu g Cd l(-1). They decreased to basal levels after 7 and 14 days of exposure. They significantly increased again after 30 days of exposure. The responsiveness of the interrenal tissue to ACTH was evaluated in vitro by monitoring the secretion of cortisol after stimulation of the head kidneys with 10(-7) M of ACTH for 10 min in perifusion. The responsiveness to ACTH of the interrenal tissue of fish exposed to 1 mu g Cd l(-1) for 2, 7 and 14 days and 5 mu g Cd l(-1) for 7 days was not significantly different from controls. On the other hand, the interrenal tissue of fish exposed to 1 mu g Cd l(-1) for 30 days secreted significantly larger amounts of cortisol in response to ACTH compared to controls. The significance of these findings to the interrenal dysfunction previously diagnosed in fish from lakes contaminated by heavy metals is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.