Increased testicular estradiol during the neonatal interval reduces Sertoli cell numbers.

Previous studies have demonstrated that reducing endogenous testicular estradiol in neonatal boars would stimulate increased proliferation of Sertoli cells during the neonatal interval. The objective of this experiment was to determine if increasing testicular estradiol would have the opposite effect of reducing Sertoli cell numbers during the neonatal interval. Five littermate pairs of boars were evaluated with one littermate receiving a silastic implant containing estradiol and the second receiving only silastic at 1.5 weeks of age. Testes were recovered at 6.5 weeks of age and Sertoli cell numbers determined. Littermates treated with exogenous estradiol had approximately two-thirds as many Sertoli cells as their control littermates (P < 0.001). This is additional evidence for regulation of Sertoli cell numbers during the neonatal interval by intra-testicular estradiol.