THE EFFECTS OF A LUTEINIZING-HORMONE-RELEASING HORMONE ANALOG ON CYTOCHROME-P450 IN RAINBOW-TROUT

Profound sex-related differences in P450 levels and P450 activities in rainbow trout trunk kidney occur during the time of spawning. Since spawning in salmonids can be induced by certain analogues of luteinizing hormone-releasing hormone (LHRH), the role of the analogue, [D-Ala(6), Pro(9)-NHEt]-LHRH (LHRH-A) in the expression of selected P450 enzymes in trunk kidney of 2-year old rainbow trout was evaluated. LHRH-A, 5 mu g/ kg, injected i.p. at days 0 and 3, reduced or abolished the expression of P450 LMC2 (P4502K1) (a catalyst for aflatoxin B-1 bioactivation and lauric acid hydroxylation) in trunk kidney of female, but not male trout, at days 10, 17, and 24. However, the expression of P4502K1 in liver of male and female trout was unchanged after LHRH-A treatment. P450 LMC1 (another catalyst for lauric acid hydroxylation) in trunk kidney and liver of both males and females was not affected by LHRH-A. No P4502K1 was detected in head kidney of control and LHRH-A-treated trout of both sexes. This study provides evidence that the expression of P4502K1 protein in rainbow trout may be affected by synthetic peptide hormones such as LHRH-A. Additional studies are being carried out to determine whether the LHRH analogue affects P4502K1 expression at the level of transcription.