RESPONSIVENESS OF THE INTERRENAL TISSUE OF YELLOW PERCH (PERCA-FLAVESCENS) FROM CONTAMINATED SITES TO AN ACTH CHALLENGE TEST IN-VIVO

The effects of chronic toxic stress on the hypothalamo-pituitary-inter renal (HPI) axis were investigated in yellow perch (Perca flavescens) captured at a reference site (Lake Memphremagog) and two sites contami nated with heavy metals and organic contaminants (ne Perrot and Iles d e la Pair, Lake St. Louis) in spring, summer, and fall. Cortisol secre tion of the fish was stimulated in situ by an acute capture stress or by an i.p. injection of 4 IU/100 g body mass of porcine corticotropin (ACTH(1-39)). The response to both these challenges was lower in perch from the highly contaminated site than in perch from the reference si te in the spring but not in summer. In fall, fish from the highly cont aminated site had, as in spring, a lower response to ACTH than fish fr om the reference site. The reduced ability of perch to respond to capt ure stress or to ACTH indicates that the interrenal tissue in fish fro m contaminated sites is functionally impaired. Cortisol-impaired fish also had abnormal carbohydrate metabolism. The reduced ability of wild fish from contaminated sites to respond to a standardized ACTH challe nge may be used as an early indicator of contamination-induced chronic stress.