Newborn and immature rat testes contain gonadotropin-releasing hormone (GnRH) receptors, and their testosterone production is stimulated by a GnRH agonist in vitro.
The possibility of direct gonadal effects of GnRH in the newborn and immature rat testis was studied by two approaches: the presence of specific high-affinity receptors for a GnRH agonist analogue (Buserelin) was studied in animals between the ages of 1 and 60 days; and the effect of Buserelin on testicular testosterone production was studied in vitro. GnRH receptors were found in the testis tissue at all ages studied, and there was a gradual increase in the number of binding sites per testis with advancing age. The highest concentration of GnRH receptors was found in the rat testis tissue on day 1 of life, 3.2 +/- 0.4 fmoles/g tissue (mean +/- SE, n = 5). The binding declined to a nadir, 1.5 +/- 0.5 fmoles/g tissue (in = 10), on day 15 post-partum (p less than 0.05), and thereafter increased again gradually to a level of 2.7 +/- 0.3 fmoles/g (n = 5) on day 60 of life (p less than 0.05). The biphasic concentration curve of GnRH receptors followed closely the volume density of Leydig cells in the developing rat testis. Buserelin at a concentration of 10(-7) M was able to stimulate significantly (p less than 0.01), by 98-146%, the testosterone production of decapsulated testes at all ages studied between 1 and 60 days of life. These results indicate the presence of functional GnRH receptors in the testis tissue of newborn and immature rats.
Huhtaniemi
I T
IT
Catt
K J
KJ
Clayton
R N
RN
D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D002064:Buserelin / Q000494:pharmacology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains / Q000254:growth & development / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000032:analysis* / Q000187:drug effects; D011966:Receptors, LHRH; D013737:Testis / Q000254:growth & development / Q000378:metabolism*; D013739:Testosterone / Q000096:biosynthesis*
D011956:Receptors, Cell Surface; D011966:Receptors, LHRH; D013739:Testosterone; D002064:Buserelin