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In the present study, we demonstrate that elevated levels of the progesterone receptor (PR)-B isoform in breast cancer cells induces down-regulation of estrogen receptor (ER) alpha mRNA and protein content, causing concomitant repression of the estrogen-regulated genes insulin receptor substrate 1, cyclin D1, and pS2, addressing a specific effect of PR/PR-B on ERalpha gene transcription. ERalpha gene promoter activity was drastically inhibited by PR-B overexpression. Promoter analysis revealed a transcriptionally responsive region containing a half-progesterone response element (PRE) site located at -1757 bp to -1752 bp. Mutation of the half-PRE down-regulated the effect induced by PR/PR-B overexpression. Moreover chromatin immunoprecipitation analyses revealed an increase of PR bound to the ERalpha-regulatory region encompassing the half-PRE site, and the recruitment of a corepressor complex containing nuclear receptor corepressor (NCoR) but not silencing mediator of retinoid and thyroid hormone receptor and DAX1, concomitantly with hypoacetylation of histone H4 and displacement of RNA polymerase II. Furthermore, NCoR ablation studies demonstrated the crucial involvement of NCoR in the down-regulatory effects due to PR-B overexpression on ERalpha protein and mRNA. We also demonstrated that the ERalpha regulation observed in MCF-7 cells depended on PR-B expression because PR-B knockdown partially abrogates the feedback inhibition of ERalpha levels after estrogenic stimulus. Our study provides evidence for a mechanism by which overexpressed PR-B is able to actively repress ERalpha gene expression.

In the present study, the molecular mechanism underlying the up-regulatory effect of estradiol (E2) on mouse insulin receptor substrate-1 (IRS-1) promoter was investigated in CHO cells on which the same promoter had first been functionally characterized. The mouse IRS-1 promoter bears four consensus half Estrogen Responsive Elements (ERE) sequences and thirteen AP-1- and ten Sp1-binding elements. We performed molecular dissection of this promoter gene providing 3' different deleted constructs, containing the same AP-1 rich region with a progressively increased number of ERE half sites located downstream. None of these constructs was responsive to E2, while a downstream region (nt -1420 to -160) rich in GC elements was induced by E2. However, the latter region lost its intrinsic E2 responsiveness when the whole IRS-1 promoter was mutated for deletion in all four ERE half sites. Deletion analysis of the ERE half sites demonstrated that only ERE located at the position -1500 to -1495, close to the GC-rich region, was able to maintain the induced activatory effect of E2 on the IRS-1 gene. Electrophoretic mobility shift and chromatin immunoprecipitation assays identified the region containing the half ERE/Sp1 (nt -1500 to -1477) as the one conferring E2 responsiveness to the whole promoter. This effect occurs through the functional interaction between E2/ERalpha and Sp1.

Progesterone, 17-hydroxyprogesterone, androstenedione, 5 alpha-dihydrotestosterone, dehydroepiandrosterone, testosterone and oestradiol concentrations in the plasma were measured by simultaneous radioimmunoassay in males of the lizard Podarcis s. sicula. Hormonal determinations were performed at monthly intervals from January to December (except for August). Testosterone and androstenedione reached peak values of 174.8 ng/ml and 21.4 ng/ml in the mating season (spring) and then testosterone fell abruptly to 5.9 ng/ml in June remaining at this level during hibernation when dehydroepiandrosterone (DHA) reached a maximal level of 28.5 +/- 9.3 ng/ml. Castration resulted in a marked decrease of testosterone, androstenedione, dihydrotestosterone and DHA values, with DHA being significantly lowered only during the winter season. In castrated animals, however, testosterone and androstenedione persisted conspicuously in the plasma during the breeding period, suggesting that adrenal sex steroid output may change during the annual reproductive cycle. In intact animals, progesterone and oestradiol exhibited peak values during the refractory period after the mating season. We suggest a probable role of oestradiol in the induction of the refractory period in this lizard.

Leydig cell function was studied in 108 varicocele (V) patients with a mean age of 30.9 years, and a control group (C) of 46 men with a mean age of 30 years. Plasma gonadotropin levels were determined before and after GNRH stimulation. Testosterone (T), 17-OH-progesterone (17-OH-P), dihydrotestosterone (DHT) and estradiol (E2) were also assayed. Mean plasma T levels were significantly decreased in varicocele patients (V = 416 +/- 12.9, n = 106; C = 487 +/- 19.9, n = 40; P less than 0.01), while the basal 17-OH-P/T ratio was significantly increased (V = 0.38 +/- 0.02, n = 56; C = 0.28 +/- 0.02, n = 40; 0.02 greater than P greater than 0.01) and remained higher after hCG stimulation (P less than 0.01). No significant differences in mean sex steroid levels were observed when comparing varicocele patients with normal sperm counts (VN) and those who had oligozoospermia (VO). There was a significant negative linear correlation between age and 17-OH-P (n = 56; r = -0.47; P less than 0.01) and T values (n = 106; r = 0.27; P less than 0.01) in varicocele patients, which contrasted with the absence of any significant correlation with age in the controls. These data suggest that the duration of idiopathic varicocele influences testicular hormone secretion.