Regulation of LH receptors and steroidogenesis in the foetal XXXX testis in vivo.

@entity35 @entity4398 @entity3566 @entity251
Foetal @entity35 were injected with high doses of @entity3566 or ovine LH (oLH) to determine if LH receptors were down-regulated and steroidogenesis impaired as is seen in the adult animal. Foetuses injected in utero with 52 micrograms/kg @entity3566 had a prompt increase in intratesticular @entity251 , demonstrating that the injected substance reached the foetal testis. Pregnant mothers were laparotomized and each foetus in one uterine horn injected with 52 micrograms/kg @entity3566 . Twenty-four hours later, the foetal testes from both uterine horns were collected and free LH receptor content measured. In foetuses injected with @entity3566 , free LH receptors were significantly reduced. LH receptors in foetal testes from the contralateral horn were not significantly different from those in controls. Foetuses injected with 52 micrograms/kg @entity3566 at 17.5 days of gestation showed a delayed response in LH receptor up-regulation when compared with neonatal @entity35 injected with comparable doses of @entity3566 . Injection of foetal and neonatal @entity35 with 400 micrograms/kg oLH showed no evidence of down-regulation, as is seen in the adult. Testes from foetuses injected with 52 micrograms/kg @entity4398 days earlier showed an increase in both basal and @entity3566 -stimulated @entity251 production during 3 h of incubation when compared with controls. These results show that the @entity35 foetal testis in vivo does not demonstrate down-regulation of LH receptors or steroidogenic lesions of the @entity251 synthetic pathway when exposed to high levels of @entity3566 as does the adult @entity35 testis. These results from the foetal testis in vivo are in agreement with results obtained from the foetal testis in vitro and the neonatal testis in vivo.
