3β-hydroxysteroid dehydrogenase-isomerase activity in placentae from pregnancies complicated by steroid sulphatase deficiency

Abstract

The 3β-hydroxysteroid dehydrogenase-isomerase activity of preparations of human placentae was determined in vitro by measuring the conversion of [ 3H]-pregnenolone to [ 3H]-progesterone. The mean activity (330 ± 40 c.p.m./mg protein/30 min, mean ± SD, n = 8) of placentae deficient in steroid sulphatase, previously stored at −20°C, was significantly less ( P < 0.001, t-test) than that of control placentae which had been treated in an identical manner (600 ± 60 c.p.m./mg protein/30 min, n = 15). However, when tested without freezing, the mean activity of the same control placentae was 2240 ± 675 c.p.m./mg protein/30 min ( n = 15) and the activity of a fresh sulphatase deficient placenta (2170 c.p.m./mg protein/30 min) was indistinguishable from that of the controls. 3β-Hydroxysteroid dehydrogenase-isomerase activity therefore appears to be sensitive to freezing and thawing and the effect is more marked in sulphatase deficient placentae. This finding confirms the earlier reports of lower activities of steroid metabolising enzymes (other than sulphatase) in steroid sulphatase deficient placentae. The results from the deficient placenta studied fresh and after freezing imply that the lower 3β-hydroxysteroid dehydrogenase-isomerase activity in steroid sulphatase deficient placentae is due to the study of tissue which had been stored at −20°C rather than of fresh tissue. Mean 3β-hydroxysteroid dehydrogenase-isomerase activity of fresh placenta from male infants was significantly less ( P < 0.05) than that of placentae where the fetus was female.