Regulation of the 3beta-hydroxysteroid dehydrogenase activity in tissue fragments and microsomes from human term placenta: Kinetic analysis and inhibition by steroids

GENTI DE RAIMONDI SUSANA; OLIVIER NORA; PATRITO LUIS; FLURY ALFREDO

PERGAMON-ELSEVIER SCIENCE LTD

Año: 1989 vol. 32 p. 413 - 413

he effects of 50pM of progesterone (P4), estradiol (Es), estrone (E,), estriol (E,), dehydroepiandrosterone (DHIA), androstenedione (A4) and testosterone (T) on the bioconversion of [3H]pregnenolone (6 nM) to [3H]P., were investigated by incubating 200 mg of tissue fragments as well as equivalent aliquots of microsomes from human term placenta during 30min. All the steroids assayed, except E, , significantly inhibited the [3H]P, formation in a microsome incubation system with respect to the control assay (P c 0.00 1). Conversely in a tissue incubation system. P4, E, as well as E3 had no effect on [3H]pregneno10ne bioconversion while E2 slightly decreased the [)H]P4 formation (P c 0.05) compared with the control. A significant inhibition was observed in this system with the other steroids (P < 0.001). To investigate these apparent different results of inhibition-noninhibition of the same steroids irrespective of the system of incubation used, the effects of P4, E, and T on 3f