INFLUENCE OF GROWTH-HORMONE ON THE HEPATIC MIXED-FUNCTION OXIDASE ANDTRANSFERASE SYSTEMS OF RAINBOW-TROUT

The effect of GH treatment on hepatic cytochrome P450 content, aryl hy drocarbon hydroxylase (AHH), aminopyrine-N-demethylase (AND), testoste rone hydroxylase, testosterone 5 alpha- and 5 beta-reductase, UDP-gluc uronyl transferase (UDPGT) and glutathione S-transferase (GST) activit ies in immature rainbow trout were investigated. Hepatic cytochrome P4 50 content, AHH and GST activities were measured in both GH implanted and GH injected animals whereas other activities were assayed in GH im planted trout only. GH implants significantly decreased cytochrome P45 0 content at 15 days compared to the control but no significant effect was observed at 15 or 30 d when GH was injected biweekly. In both cas es, AHH activity was significantly decreased by GH treatment compared to the control whereas GST remained unchanged. Compared to the control , GH implanted fish exhibited a pronounced inhibition of AND, a decrea sed 6 beta and 16 beta-testosterone hydroxylation, an inhibition of UD PGT with testosterone as substrate and an enhanced 17 beta-testosteron e oxidation.