Effect of developmental age or time after transplantation on Sertoli cell number and testicular size in inbred Fischer rats

The objectives were to establish the developmental age of Fischer rats at which the Sertoli cell number is stabilized, to establish the normal reference plateau number of Sertoli cells for evaluation of testes after transplantation, and to determine whether the developmental pattern establishing Sertoli cell proliferation and stability are similar between intact and transplanted testes. Sertoli cell number was determined at ages 10-120 days in intact rats and at various times (10-90 days) after transplantation of prenatal or neonatal testes. Testes were fixed by vascular perfusion or by immersion with 2% glutaraldehyde and immersion in 1% osmium and were embedded in Epon 812. Sections and serial sections were cut at 0.5 micrometers to determine the Sertoli cell nuclei volume density and the volume of an individual Sertoli cell nucleus by brightfield microscopy or at 20 micrometers to determine the maximum height and width of nuclei. A correction factor was calculated for intact (0.663 +/- 0.025) or for transplanted (0.558 +/- 0.029) testes to determine the volume of a single Sertoli cell nucleus from height and width measurements. In intact testes, Sertoli cell numbers significantly increased to Day 20 but were not different between 15 and 90 days. Sertoli cell number in prenatal or neonatal transplanted testes increased to 20 or 30 days posttransplantation and then stabilized to Day 60 or 90. There was no difference in the plateau number of Sertoli cells per rat between prenatal and neonatal testes. Sertoli cells in 10-day- and 30-day-transplanted testes incorporated 3H-thymidine when placed in culture. A few tubules had complete spermatogenesis at 90 days posttransplantation, indicating that Sertoli cells in some of these tubules were functional. Leydig cell structure appeared to be normal. Leukocytic infiltration of testes was not observed in intact rats or in rats receiving neonatal testes. Although transplanted testes showed a delay in reaching the plateau value for Sertoli cell number per testis and although the value reached was lower, the developmental pattern of Sertoli cell proliferation in transplanted testes was similar to that in intact rats.