Steroidglucuronyltransferases, V. Formation and Hydrolysis of Oestrogen Glucuronides by the Liver, Kidney and Intestine of the Pig

Abstract

The glucuronidation of oestrone, oestradiol-17ß and oestriol by the 600 g supernatant fraction of pig liver, kidney and intestine was studied in the presence and absence of UDPglucuronic acid. All three tissues formed only the 3-glucuronides of the oestrogens incubated. The order of glucuronidation with oestrone and oestradiol-17ß as substrates was kidney/intestine> liver. The 3-glucuronides of oestrone, oestradiol-17ß and oestriol were hydrolysed at pH 5.0 by the 600 xŝ upernatant fractions of the three tissues to a considerable extent. The order of activity was liver> intestine> kidney. These studies show that liver, kidney and intestine of the pig specifically glucuronidate the phenolic hydroxyl group at C-3 of oestrone, oestradiol-17ß and oestriol and also specifically hydrolyse the 3-glucuronides. The liver exhibited significant 17ß-hydroxysteroid oxidoreductase activity, followed by the kidney, while the intestine was devoid of such activity. However, no conversion of oestrone 3-glucuronide to oestradiol-17ß 3-glucuronide or vice versa was observed.

Steroid glucuronyltransferases of rat liver. Properties of oestrone and testosterone glucuronyltransferases and the effect of ovariectomy, castration and administration of steroids on the enzymes

“…In studies in vitro, foreign compounds such as p-nitrophenol, o-aminophenol and phenolphthalein have often been used as substrates for glucuronyltransferases to measure enzyme activity (Dutton, 1971;Winsnes, 1973). Endogenous substrates include bilirubin (Mulder, 1972) and steroid hormones such as oestrone, oestradiol-17.8, oestriol, testosterone (Rao & Breuer, 1969;Rao et al, 1970a Rao et al, ,b, 1972Rao et al, , 1974Gotze et al, 1971) and tetrahydrocorticosterone (Miller et al, 1973). With so many different acceptors, it may be asked what degree of specificity UDPglucuronyltransferase possesses.…”