Effects of gonadotrophins on the proliferative activity of somatic testicular cells in neonatal and prepubertal rats.

The proliferative activity of the different testicular somatic cell lineages was studied in neonatal and prepubertal rats after treatment with recombinant FSH (recFSH) and human chorionic gonadotrophin (hCG). Male rats were treated on days 5-9 or 15-19 with 1 or 3 IU/rat.day, respectively, of recFSH, 10 IU/rat.day of hCG or vehicle and sacrificed the day following the last injection. Proliferation was studied by the immunohistochemical demonstration of DNA-incorporated 5-bromodeoxyuridine (BrdU) in both paraffin- and Epon-embedded tissues. No differences existed for the labeling indices in paraffin- or Epon-embedded tissues, but the identification of some cell types were easier in these latter one. At 10 days of age, no significant differences were found for the proliferative activity of the different cell types, except for the labeling index of foetal Leydig cells that was increased in hCG-treated animals. At 20 days of age, treatment with recFSH increased the testicular weight and tubule diameter, as well as the size of adult type Leydig cells and the labeling index of macrophages. Treatment with hCG increased the testicular weight and the number and size of adult-type Leydig cells, as well as the labeling indices of mesenchymal, adult-type Leydig cells and macrophages. These results indicate that the effects of gonadotrophin treatment on the different somatic testicular cell types are dependent on both the type of cells and their developmental stage.