To our knowledge this is the first report on the changes in GH-R in testicular tissue during a spermatogenetic cycle in a vertebrate. Relatively large numbers of GH-R were present in the immature trout testis, that is, before any sign of spermatogenetic development could be detected. At that stage, somatic cells and stem germ cells (or A spermatogonia) are believed to proliferate as the gonad grows slowly. We demonstrated that changes in GH binding observed during the reproductive cycle resulted from a progressive change in the capacity of GH-R, with no alteration in their affinity. buy prednisone
We found that GH-R concentration in the testis was maximum at the beginning of spermatogenetic development (B spermatogonia proliferation), decreased progressively but markedly during the advance of meiosis, and became minimal at the end of spermatogenesis. These data suggest that GH could be potentially important for gonadal functions during the first steps of spermatogenesis. While no similar study has previously been undertaken in male vertebrates, one quantitative report shows that GH-R/GH-BP mRNA concentration decreases between 1 and 5 wk of age in the rat ovary and is constant during the estrous cycle.