Changes in hepatic and testicular GH-R concentration were quite different, suggesting that the evolution observed in these two organs did not have the same causes. This is in agreement with recent studies in higher vertebrates demonstrating that the regulation of GH-R expression is tissue specific. Hepatic GH-R have been found to be either up- or down-regulated by plasma GH in mammals (reviewed in ). In teleost fish, regulation of hepatic GH-R by high plasma GH has also been reported. In our study, variations in testicular or hepatic GH-R did not appear related to changes in plasma GH concentration. buy antibiotics online
In particular, the decrease in testicular GH-R concentration observed during spermatogenesis may not be related to down-regulation or to binding site occupation by endogenous GH, as the level of this hormone is low and does not vary during most of the cycle. Nevertheless, elevated GH levels found in spawning males have been previously reported , and we cannot exclude the possibility that this change is related to the high binding capacity observed in the liver of these males.