Control of testicular steroidogenesis in foetal rat: effect of decapitation on testosterone and plasma luteinizing hormone-like activity

Abstract

These studies were designed to investigate the regulation of testicular testosterone and the role of the hypophysis during the last 5 days of gestation in the rat. Plasma LH-like activity was measured by bioassay and testosterone by radioimmunoassay. In both sexes, plasma LH-like activity levels were low on days 17.5 and 18.5 (< 0. 10\ p=n-\ 0. 26 ng/ml) and rose on day 19.5 (0.10\p=n-\1.25 ng/ml). Thereafter the levels increased considerably and were significantly higher in females than in males: on day 21.5 they reached 0.44\p=n-\2.42 ng/ml in males and 2.20\p=n-\3.96 ng/ml in females. Plasma levels of testosterone were significantly higher in males than in females and were maximal on day 18.5 in males. Testicular content of testosterone reached maximum values on day 18.5 and remained constant thereafter. Foetal decapitation clearly reduced testicular production of testosterone and plasma LH-like activity only after day 19.5. A residual gonadotrophic activity was detected at all stages in decapitated foetuses from both sexes (< 0.10\p=n-\0.46 ng/ml). These results suggest that pituitary LH secretion and pituitary-testicular interrelationships are essentially established between day 19.5 and 20.5, and that the ageing testis becomes more dependent on gonadotrophic stimulation. The existence of an extrapituitary LH-like activity might indicate the presence of placental gonadotrophins.We recently reported that testicular production of testosterone can be decreased by hypophysectomy at the end of gestation in rat foetuses (Naessany et al. 1981). This observation suggests that the foetal hypophysis plays a main role in the control of steroidogenic activity of the testes although clear cut observations were not obtained by other au¬

Pituitary-Gonadal Interactions in Perinatal Rats: Relationships of Plasma Luteinizing Hormone and Testosterone Concentrations, and Pituitary Levels of LH Subunit mRNAs

“…The new assay also makes studies on rat fetal gonadotropin secretion practically easier by reducing the number of animals needed for representative data. Our results on plasma LH concentrations agree well with those performed earlier on pools of fetal plasma [8,12,21], Fig. 4.…”

“…Injection of T to pregnant rats causes a decrease in testicular T of male fetuses from day f 19.5 onwards, as a sign of functional negative feedback [11], Fetal decapitation reduces basal in vitro secretion of testicular T from day f20.5 onwards [12,13], and on day f22.5, but not on day f20.5, plasma T concentration is decreased [13]. Castration on day f 19.5 causes a 2-fold increase within 24 h in the serum LH-like bioactivity, and decapitation at the same time point decreases this activity [ 14], Taken together, the above results suggest that the gonadal negative feedback regulation of pituitary function develops in the male rat during the last 3 days of gestation.…”

Maternal Exposure to Dioxin Disrupts Gonadotropin Production in Fetal Rats and Imprints Defects in Sexual Behavior

“…Thus, fetal brain depends on the testis for the supply of testosterone, an estrogen precursor, for its development. In connection with this issue, previous works have suggested that testosterone production in male fetal rats is independent of LH-mediated regulation until GD19.5 (Habert and Picon, 1982;El-Gehani et al, 1998). This is based on the evidence that although fetal testicular testosterone occurs at approximately GD15, and its concentration increases sharply at GD18, plasma LH does not occur until GD19.5.…”

Effect of beta-carotene on titanium oxide nanoparticles-induced testicular toxicity in mice

“…Serum testosterone concentration was measured by radio immunoassay (RIA) method. Testosterone was also extracted from testes as previously described [29]. Briefly, testes were homogenized by sonication and centrifuged at 5,900 × g for 5 min.…”