ONTOGENY AND HORMONAL BASIS OF FEMALE-DOMINANT RAT HEPATIC SULFOTRANSFERASES

Female-dominant sulfotransferases (ST) are a group of enzymes catalyzi ng sulfation of steroid hormones, bile acids and exogenous carcinogens . To understand the regulation of these enzymes, developmental and hor monal regulation of three female-dominant ST was studied. The three ST , ST-20/21, ST-40/41 and ST-60, were differentiated by specific oligon ucleotide probes, and their gene expression was examined by Northern-b lot analyses. The three ST have different developmental patterns, as S T-20/21 and ST-60 were increased after puberty in female rats, althoug h ST-40/41 was higher in immature rats. In addition, ST-20/21 and ST-6 0 expression reached a peak at 30 days of age in male rats, although S T-40/41 reached its highest value in male rats at 15 days of age. Estr ogens and androgens did not appear to be major determinants of the dev elopmental profiles. However, ST-20/21 was decreased in both male and female rats by hypophysectomy, and reversed by continuous infusion (fe male pattern) of growth hormone (GH). In contrast, hypophysectomy elev ated ST-40/41 and ST-60 expression in males. The elevation in males wa s reversed by GH injection (male pattern). This study demonstrates tha t the three female-dominant sulfotransferases display two ontogenic pa tterns and are regulated by different mechanisms. Female GH secretory pattern appears to determine the high expression of ST-20/21 in postpu bertal female rats, although male GH secretory pattern results in the low expression of ST-40/41 and ST-60 in mature male rats.