Reduced Endogenous Estrogen and Hemicastration Interact Synergistically to Increase Porcine Sertoli Cell Proliferation1

Reduced endogenous estrogen and hemicastration both stimulate proliferation of porcine Sertoli cells. The objective of these experiments was to compare the temporal pattern of response to each stimulus and the response to the combined stimuli as indications of shared or separate mechanisms. Within a replicate, one littermate was treated weekly with the canola oil vehicle and remained intact, one littermate was treated weekly with the vehicle and one testis was removed at day 8, one littermate was treated weekly with the aromatase inhibitor letrozole to reduce endogenous estrogens and remained intact, and the fourth littermate was treated weekly with letrozole and one testis was removed at day 8. Four replicates were evaluated at 2 wks of age, five replicates evaluated at 6.5 wks of age, and five replicates evaluated at 11 wks of age with treatment ceasing at 6 wks of age. Sertoli cell numbers were determined following GATA4 labeling using the optical dissector method. Estradiol, estrogen conjugates, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and inhibin were determined by radioimmunoassay. Hemicastration appeared to have a rapid effect on Sertoli cell proliferation but letrozole treatment had no apparent effect on Sertoli cell numbers at 2 wks of age. Both letrozol