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 3 β-hydroxysteroid dehydrogenase/ Δ 5- Δ 4 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.
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