Demonstration of gonadotropin-induced plasma renin activity in human internal spermatic vein

In order to investigate the secretion of renin from the Leydig cells of human testis, plasma renin activity (PRA) in left internal spermatic vein (ISV) and cubital vein (CV) was measured at the time of surgical repair of varicocele in 19 patients aged from 21 to 39 years. Ten of them were given a single im administration of hCG (10,000 IU/m2) 4 days before the operation, whereas the remaining nine were not treated. Although mean PRA levels in CV in treated and non-treated groups were similar (1.25 +/- 0.45 and 1.14 +/- 0.38 nmol/l per h, respectively), mean PRA level of ISV in the treated group (3.52 +/- 0.76 nmol/l per h) was significantly higher than that in the non-treated group (1.30 +/- 0.32 nmol/l per h) (P less than 0.01); serum testosterone levels in the same ISV were also much higher in the treated than in non-treated group (P less than 0.001). These data show the following results; 1) under basal conditions, no release of renin from Leydig cells into testicular blood flow could be observed; 2) after treatment with hCG, the secretion of renin into the ISV seemed to be demonstrable. The present results suggest for the first time the secretion of hCG-induced renin from the human testis in vivo.