SEX-DIFFERENCES IN CYTOCHROME-P-450-DEPENDENT XENOBIOTIC AND STEROID-METABOLISM IN THE MATURE RAINBOW-TROUT KIDNEY

The rainbow trout kidney during the late reproductive stages was found to exhibit a profound sex-related difference in its capacity to metabolize both xenobiotic model substrates and endogenous steroids. The cytochrome P-450 content of trunk kidney microsomes was 28-fold higher in males than in females. In trunk kidney microsomes, the dealkylation of various 7-alkoxycoumarins was 22- to 38-fold higher in males than in females, whereas ethylmorphine-N-demethylase (EMND) and 7-ethoxyresorufin-O-deethylase (EROD) activities were only slightly higher in males than in females. In contrast to the alkoxycoumarin- and EROD activities, the EMND activity showed considerable activity in the head kidney microsomes and the level was found to be higher in females than in males. Progesterone and androstenedione 16- and 6β-hydroxylase activities were present mainly in the male trunk kidney microsomes. On the contrary, the oestradiol 2-hydroxylase was distributed along the whole kidney and showed a 2.8-fold higher activity in the female head kidney than in the male head kidney. The catalytic analysis indicated a differential regulation of trout renal P-450 isoenzymes during sexual maturation. Furthermore, the data presented indicate that the high level of the hemoprotein in male trunk kidney was not a general increased level of the protein, but rather an increase of certain cytochrome P-450 isoenzymes.