Abstract

The ontogenic and hormonal regulation of a sulfotransferase, SULT1B1, was examined. Hepatic RNA was isolated from rats of various ages from 1 to 90 days. The mRNA for SULT1B1 is low for both sexes until a dramatic increase (∼6-fold) occurs between 15 and 30 days of age in male rats. SULT1B1 expression then decreases to half of the maximal level by 90 days of age. The increase in SULT1B1 mRNA in female rats is less dramatic and occurs between 30 and 45 days of age. SULT1B1 mRNA expression plateaus from 45 to 90 days in female rats. Expression of SULT1B1 mRNA is comparable in adult male and female rats. RNA was isolated from hypophysectomized (HX) animals and HX animals treated with growth hormone [by either male (injection) or female (infusion) pattern], estradiol, progesterone, or testosterone. HX and HX plus growth hormone, or HX plus steroid replacement, did not alter SULT1B1 mRNA expression. Pituitary-intact rats were treated with steroidal compounds dexamethasone (DEX) and pregnenolone-16α-carbonitrile (PCN). Both DEX and PCN increased expression of SULT1B1 mRNA in male rats (4- and 3-fold, respectively). However, in female rats, only PCN induced SULT1B1 mRNA (2-fold), whereas DEX did not induce SULT1B1 in female rats. Analysis of SULT1B1 protein expression indicated that only when SULT1B1 mRNA was markedly increased, that is in DEX-treated male rats, was SULT1B1 protein increased. Thus, although adult male and female rats have similar SULT1B1 mRNA expressions, the patterns develop ontogenically differently. SULT1B1 is not regulated by pituitary hormones and DEX induces SULT1B1 protein in male rats.