Follicle-Stimulating Hormone Activation of Glycogen Phosphorylase in the Sertoli Cell-Enriched Rat Testis*

The potential role of glycogen phosphorylase in providing energy for the Sertoli cell-enriched testis has been investigated. This enzyme is detectable in testes from rats 6–54 days of age. Glycogen phosphorylase in isolated Sertoli cellenriched testes is specifically stimulated by FSH. Maximal activation (2-fold) is obtained within 10 min after adding 0.5 μg FSH/ml to isolated immature testes (16 days old). There is only a 1.1-fold activation by FSH in testes from mature (34 days old) animals. The sensitivity to the gonadotropin can be restored by adding l-methyl-3-isobutylxanthine, a phosphodiesterase inhibitor, with the FSH. Phosphorylase can be activated by effectors that mimic the actions of the two proposed mediators of FSH action, cAMP and Ca+2. Phosphorylase from testis of either age is maximally activated by an analog of cAMP, 8-bromo-cAMP. While phosphorylase is rapidly activated 1.4-fold by incubating isolated testis for 2 min with A23187, a Ca+2 ionophore, the age, time, and dose dependence of FSH activation are consistent with conversion mediated by cAMP. Phosphorylase was localized in cultured Sertoli cells by indirect immunofluorescence microscopy. Affinity-purified antiphosphorylase decorated cytoskeletal structures that resemble stress fibers, suggesting that phosphorylase may function in Sertoli cells to provide energy for cytoskeletal motility. (Endocrinology113: 1476, 1983)