Demonstration of a Pituitary Gonadotrophin Hormone Activity in the Male Foetal Mouse

Abstract

The testosterone production by 18-days-old foetal mouse testis was measured in an organ culture system, by RIA in the culture medium. This production was time-dependent, and could be stimulated by ovine LH and age-matched foetal pituitary. The gonadotrophin activity derived from foetal pituitary appeared to be released into the culture medium as a limited reserve. These data clearly show that a biologically active gonadotrophin material is present in the pituitary of the 18-days-old mouse foetus.In rodents, the male gonad exhibits hormonal activity as soon as the genital ducts undergo differentiation. Castration experiments in the mouse embryo (Raynaud 8c Frilley 1946, 1947a have demonstrated that early testicular secre¬ tion^) are responsible for the development of male genital tract and accessory glands. The 12-days-old foetal mouse testis synthetizes testosterone (T) in vitro from radioactive precursors (Weniger 8c Zeis 1972). This T synthesis is main¬ tained in the later steps of foetal development, as shown by labelled precursors experiments (Block et al. 1971;Pointis et al. 1972; Weniger 8c Zeis 1974) and by radioimmunoassay (Pointis 8c Mahoudeau 1974).The role of the foetal pituitary on the testis development and secretion(s) is not clear. Decapitation of the rabbit foetus, performed before the period of genital duct differentiation, results in testicular deficiency which can be sup¬ pressed by gonadotrophin administration (Jost 1951). In contrast, in rats (Wells

Embryonic gonadotropin-releasing hormone signaling is necessary for maturation of the male reproductive axis

“…Alternatively, LH may induce FSHβ expression through gonadal testosterone feedback (Fig. S6B) (8)(9)(10)(11). New FSH+ cells are continuously born postnatally and accumulate over time in the mutant mice (Fig.…”

“…At this stage, the fetal pituitary gland becomes GnRH responsive (8). Furthermore, fetal testes can secrete steroid hormones in response to LH at E16 (8)(9)(10)(11), raising the possibility that an initial increase in LH secretion may be triggered by GnRH at this developmental stage.…”

Hypothalamic control of the male neonatal testosterone surge

“…LH was able to stimulate the synthesis and secretion of testosterone from rat testes as young as E14.5. Cultured testes from E18 mice also increase testosterone secretion in response to LH application; moreover, co-culture of the testes with pituitary glands increased testosterone secretion [37]. Furthermore, the pituitary glands of male but not female rats were shown to have elevated concentrations of LH between E17 and E20 [38].…”

Effect of Luteinizing Hormone (LH) and LH-Releasing Hormone (LHRH) on Testosterone Production <i>In Vivo</i>, in Fetal Rabbit Testis in Late Gestation

“…What regulates testosterone synthesis in the fetal and newborn rabbit? Gonadotrophins (LH or HCG) or the embryonic pituitary gland stimulate testosterone production by the fetal testis in vitro in the rat (16,10), the mouse (11,12) and the monkey (5). Testosterone secretion by the embryonic testis is stimulated in vivo by LHRH in the monkey (5) and the bull (8).…”