Jacques Couet

Rapid modulation of ovarian 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase gene expression by prolactin and human chorionic gonadotropin in the hypophysectomized rat

Abstract In order to better understand the role of prolactin (PRL) and luteinizing hormone (LH) on progesterone biosynthesis in the ovary, we have investigated the time course (1–9 days) of the effect of PRL and human chorionic gonadotropin (hCG) on ovarian 3β-hydroxysteroid dehydrogenase/ Δ 5 - Δ 4 isomerase (3β-HSD) expression in the hypophysectomized rat. As evaluated by quantitative in situ hybridization using a 35 S labelled type I 3β-HSD cDNA probe, the administration of hCG for 2, 3 and 9 days induced increases of 63%, 145% and 146% above control, respectively, in 3β-HSD mRNA levels in ovarian interstitial cells. The absence of apparent effect of the gonadotropin in other ovarian cell types could explain the small modulation of ovarian 3β-HSD protein content and enzymatic activity observed in total ovarian tissue. On the other hand, treatment with PRL caused a rapid decrease in 3β-HSD mRNA levels in corpus luteum by 23%, 63%, 76% and 78% ( P 14 C]dehydroepiandrosterone into [ 14 C]androstenedione. The inhibitory effect of PRL on 3β-HSD expression and activity is correlated with a progressive decrease in serum progesterone concentration from a pretreatment value of 4.8 nM to levels below the limit of detection (

Effects of human chorionic gonadotropin (hCG) and prolactin (PRL) on 3β-hydroxy-5-ene-steroid dehydrogenase/Δ5-Δ4 isomerase (3β-HSD) expression and activity in the rat ovary☆

Abstract Using a recently cloned rat ovary 3β-HSD cDNA and antibodies raised against purified human placental 3β-HSD, we have studied the effects of treatment with human chorionic gonadotropin (hCG) and hyperprolactinemia achieved by pituitary implants, alone or in combination, on the expression and activity of ovarian 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase (3β-HSD) in intact adult rats. 32P-and 35S-labeled cDNA probes were used to evaluate the effects of treatments on 3β-HSD mRNA levels by dot blot and in situ hybridization, respectively, while enzymatic activity was measured by the conversion of [14C]dehydroepiandrosterone into [14C]androstenedione. The present data show that hCG exerts a marked trophic effect on rat corpora lutea with an increase in total ovarian 3β-HSD mRNA levels, 3β-HSD protein content as well as enzymatic activity, resulting in an increase in serum progesterone levels. Prolactin-secreting pituitary implants alone, on the other hand, while exerting small effects on 3β-HSD expression and activity, led to a marked potentiation of the stimulatory effect of hCG on all parameters. The present data show that hCG and PRL act synergistically to stimulate ovarian progesterone secretion via an increase in 3β-HSD mRNA levels, protein content and enzymatic activity.