DISTRIBUTION OF HYDROXYSTEROID DEHYDROGENASES IN THE PLACENTA OF THE PIG

Abstract

SUMMARY The presence of hydroxysteroid dehydrogenases in the pig placenta and associated uterine structures is described between 26 days of gestation and term. Activity with androsterone, aetiocholanolone, DHA, pregnenolone, 17α-hydroxypregnenolone, 3β-hydroxy-5β-androstan-17-one, cortisol, 3β,16β-dihydroxyandrost-5-ene 3-methyl-ether, 3,16β-dihydroxyoestra-1,3,5(10)-triene 3-methyl-ether, oestradiol-17β, and 20β-hydroxyprogesterone in the trophoblast increased in mid-pregnancy, and thereafter decreased towards term, except with androsterone, cortisol, 3β,16β-dihydroxyandrost-5-ene 3-methyl-ether, 3,16β-dihydroxyoestra-1,3,5(10)-triene 3-methyl-ether and oestradiol whose increased level of activity persisted. No activity was found in the trophoblast with 1 1β-hydroxyandrostenedione, 3β-hydroxyandrost-5-en-16-one 3-methyl-ether, 17α-oestradiol, testosterone, or 20α-hydroxyprogesterone. Activity in the trophoblast of the areolae was consistently absent or greatly decreased. In the maternal epithelium, intense activity with oestradiol-17β, and testosterone as substrates (but no others) was observed early in pregnancy, but decreased markedly later. Activity was consistently higher in the epithelium related to the opening of the areolae. No other uterine or foetal structures gave a positive reaction. Some attempt is made to correlate the presence of the enzymes with their function, with biochemical findings regarding isolation of steroids from the placenta, and with the effects of ovariectomy on pregnancy in the pig.