Human placental Δ5-3β-hydroxysteroid dehydrogenase, Δ4,5isomerase: in vitro effect of dehydroepiandrosterone and allylestrenol

The in vitro effects of dehydroepiandrosterone (DHA) and allylestrenol on human placental Δ5-3β-hydroxysteroid dehydrogenase, Δ4,5 isomerase activity (Δ5-3β-HSDH) was investigated by incubation of subcellular fractions with [4-14C] pregnenolone. It has been found that DHA inhibits the Δ5-3β-HSDH activity up to −81% at 5×10−5M concentration while allylestrenol seems to be able to lightly stimulate the Δ5-3β-HSDH activity with a maximum effect (+15–26%) at 5×10−7M concentration. The data concerning allylestrenol, seem of particular interest as this compound is used as a progestative drug during pregnancy, if one consider the inhibitory effect exerted by several natural and synthetic steroids on the Δ5-3β-HSDH activity.