EFFECTS OF GONADOTROPINS ON THE PROLIFERATIVE ACTIVITY OF SOMATIC TESTICULAR CELLS IN NEONATAL AND PREPUBERTAL RATS

The proliferative activity of the different testicular somatic cell li neages was studied in neonatal and prepubertal rats after treatment wi th recombinant FSH (recFSH) and human chorionic gonadotrophin (hCG). M ale rats were treated on days 5-9 or 15-19 with 1 or 3 IU/rat.day, res pectively, of recFSH, 10 IU/rat.day of hCG or vehicle and sacrifized t he day following the last injection. Proliferation was studied by the immunohistochemical demonstration of DNA-incorporated 5-bromodeoxyurid ine (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 latte r one. At 10 days of age, no significant differences were found for th e proliferative activity of the different cell types, except for the l abeling index of foetal Leydig cells that was increased in hCG-treated animals. Ar. 20 days of age, treatment with recFSH increased the test icular weight and tubule diameter, as well as the size of adult-type L eydig cells and the labeling index of macrophages. Treatment with hCG increased the testicular Freight and the number and size of adult-type Leydig cells, as well as the labeling indices of mesenchymal, adult-t ype Leydig cells and macrophages. These results indicate that the effe cts of gonadotrophin treatment on the different somatic testicular cel l types are dependent on both the type of cells and their developmenta l stage.