Testicular 3 alpha-hydroxysteroid oxidoreductase activity in the developing male rat

Effect of erythropoietin on Leydig cell is associated with the activation of Stat5 pathway

In order to elucidate whether erythropoietin (EPO) influences male reproduction, EPO activation via erythropoietin receptor (EPOR) of Stat5 was studied in Leydig cell cultures. RT-PCR analysis of mRNA that had been prepared from primary rat Leydig cell culture and the mouse Leydig tumor cell line (I-10 cells) each demonstrated amplification of the appropriate fragment for the respective genes. Both I-10 cells and primary rat Leydig cell cultures were treated with 1U/ml recombinant human erythropoietin (rHuEPO) for various time periods upto 60 min, and cytoplasmic proteins, total cellular proteins, and nuclear extracts were isolated. Expression of Stat5b protein and phosphorylated Stat5b protein were investigated by Western blotting using anti-Stat5b pAb and anti-phospho-Stat5a/b pAb. Stat5b protein exists at the cytoplasmic level irrespective of exposure to rHuEPO, while phosphorylated Stat5b protein increases upon rHuEPO stimulation. DNA binding of nuclear protein to synthetic double-stranded oligonucleotides containing a DNA response element derived from PRL-inducible element (PIE) was examined using a gel mobility shift assay. The oligonucleotide representing the PIE of the rat beta-casein promoter was demonstrated to bind to the nuclear extract of rHuEPO-treated cells, time dependently forming a single mobility shift complex X. These data suggest that EPO binds to a receptor expressed on the surface of Leydig cells. This EPOR regulates expression of specific gene, through a Jak-Stat pathway to influence male reproductive function.

Studies on the developmental pattern of rat ovarian 3 alpha-hydroxysteroid dehydrogenase: inhibition of the postpubertal activity with medroxyprogesterone acetate in vivo

The developmental pattern of rat ovarian 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD) activity was determined with respect to age, vaginal opening, ovarian histology and serum 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-diol). The enzyme was assayed by the incubation of [3H]dihydrotestosterone with a portion of whole ovarian cytosol in the presence of 5 X 10(-4) M NADPH. Serum levels of 3 alpha-diol declined from 11.1 +/- 1.2 ng/ml on day 22-3.4 +/- 0.3 ng/ml on day 30 (P less than 0.01). There was no significant change in 3 alpha-HSD during that period which fluctuated from 6.0 +/- 4.0 nmol/h/organ on day 22-8.4 +/- 1.9 nmol/h/organ on day 39. A significant increase on day 42 of 21.1 +/- 6.1 nmol/h/organ occurred well after vaginal opening, corpus luteum formation and the presence of ovarian progesterone; the activity plateaued on day 49 at 31.2 +/- 3.7 nmol/h/organ. In an attempt to inhibit the developmental increase in 3 alpha-HSD activity, medroxyprogesterone acetate (MPA), known inhibitor in vitro was administered to three groups of developing rats in vivo. The administration of MPA at doses of 0.1, 1.0 and 10.0 mg/kg to 30 and 36 day did not inhibit activity when assayed on day 44. In 44-day old rats, the administration of MPA failed to inhibit 3 alpha-HSD activity at 24 h (C-21.1 +/- 2.6; 0.1 mg/kg-19.4 +/- 5.5; 1.0 mg/kg-20.7 +/- 3.7; 10.0 mg/kg-21.1 +/- 3.0 nmol/h/organ) yet there was a significant reduction of 3 alpha-HSD activity when assayed at 48 h (C-21.1 +/- 1.5; 01 mg/kg-9.6 +/- 1.3; 1.0 mg/kg-8.5 +/- 1.9; and 10 mg/kg 5.2 +/- 2.0 nmol/h/organ).

Inhibitory effect of gonadotropin releasing hormone upon cultured testicular cells

The direct inhibitory of gonadotropin-releasing hormone (GnRH) upon testicular androgen production was studied in cultured testicular cells. Enzyme-dispersed testicular cells from immature hypophysectomized rats were cultured for 6 days in a serum-free medium with or without various hormones. Culture media were changed every 2 days and media concentration of a androgens was measured by radioimmunoassay. The testis cultures from immature rats secrete predominately 5 alpha-androstane-3 alpha, 17 beta-diol (A-diol) and androsterone but negligible amounts of androstenedione, testosterone and dihydrotestosterone. Incubation of testicular cells with hCG and FSH increased A-diol and androsterone production as compared to control cultures. In contrast, treatment with GnRH or a GnRH agonist (des-Gly10, D-Leu6 (N alpha Me)Leu7, Pro9NHEt-GnRH) inhibited the gonadotropin effect in a dose-dependent manner; 10(-8) M GnRH inhibited A-diol production by approximately 20% on day 4 and 6 of culture whereas 10(-6) M GnRH inhibited A-diol production by greater than 80%. The observed effect of GnRH upon testicular cells in primary culture demonstrates that the hypothalamic peptide directly inhibits testicular steroidogenesis.