Human placental delta 5-3 beta-hydroxysteroid dehydrogenase, delta 4,5 isomerase: in vitro effect of dehydroepiandrosterone and allyestrenol.

The in vitro effects of dehydroepiandrosterone (DHA) and allylestrenol on human placental delta 5- 3 beta-hydroxysteroid dehydrogenase, delta 4,5 isomerase activity (delta 5-3 beta-HSDH) was investigated by incubation of subcellular fractions with [4-14C] pregnenolone. It has been found that DHA inhibits the delta 5-3 beta-HSDH activity up to -81% at 5 X 10-5 M concentration while allylestrenol seems to be able to lightly stimulate the delt a 5-3 beta-HSDH activity with a maximum effect (+15-26%) at 5 X 10-7 M 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 delta 5-3 beta-HSDH activity.