Morphological and metabolic changes in common carp, Cyprinus carpio, during short-term copper exposure: Interactions between Cu2+ and plasma cortisolelevation

The effects of increased endogenous cortisol levels were compared with thos e of sublethal copper exposure in the freshwater common carp, Cyprinus carp io. Fish were exposed to either increased levels of endogenous cortisol (20 0 ng/ml) or sublethal copper (1.9 muM) alone or were pretreated by elevatin g plasma cortisol levels prior to copper exposure to assess whether interac tions between both treatments occurred. Effects induced by increased cortis ol levels included increased Na+/K+-adenosine triphosphate (ATPase) activit y and increased plasma Na+ and plasma osmolarity, while copper exposure ind uced anaerobic metabolism, gill damage, decreasing Na+/K+-ATPase activity, decreasing plasma ion levels, and blood thickening. Pretreatment of copper- exposed fish with cortisol partially protected these fish by reducing the c opper-induced decrease in Na+/K+-ATPase activity. Overall, the results obta ined in this study argue against a major role for cortisol as an intermedia te for the toxic effects of copper.