Ontogenesis of the in vitro response of rat testis to gonadotropin-releasing hormone.
The age-related evolution of the in vitro effects of a gonadotropin releasing hormone agonist ([D-Trp6]-GnRH) on the secretion of testosterone by the testis, cultured during 3 days on a Millipore filter floating on M199 medium, was studied during the perinatal period in the rat. The basal and luteinizing hormone (LH)-stimulated secretions by testes explanted on fetal day 14.5 were unaffected by the agonist. With fetal testes explanted on days 16.5 and 18.5 post-conception, the agonist inhibited, in a concentration-dependent manner, both basal and LH-stimulated secretions from the second or the third day of treatment onwards. With fetal and neonatal testes explanted on days 20.5, 21.5 and 31.5 post-conception, the GnRH agonist also had a long-term inhibitory effect on LH-stimulated secretion, but increased basal secretion. This stimulatory effect was already observed after 4 h of culture, and was maintained for 3 days. These results suggest that, during fetal development, the cellular mechanisms involved in the negative testicular response to GnRH are differentiated 3-5 days before those involved in the positive response. Lastly, after 3 days of preculture in hormone-free medium, fetal testes explanted on day 14.5 displayed long-term GnRH agonist inhibition of in vitro basal secretion of testosterone. This observation points out a spontaneous differentiation of the negative responsiveness to GnRH in the cultured fetal testis.
Habert
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Laboratoire de Physiologie du Developpement, CNRS URA 307 and INSERM U 307, Université Paris 7, France.
Devif
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Gangnerau
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Lecerf
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D000818:Animals; D002454:Cell Differentiation; D007987:Gonadotropin-Releasing Hormone / Q000502:physiology*; D008297:Male; D009924:Organ Culture Techniques; D051381:Rats; D011919:Rats, Inbred Strains; D013737:Testis / Q000166:cytology / Q000196:embryology* / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism
D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone