Inhibition of protein kinase C by staurosporine increases estrogen secretion by rat Sertoli cells
Lambert A., Talbot JA., Mitchell R., Robertson WR.
<jats:title>Abstract</jats:title> <jats:p>We have examined the effect of inhibition of protein kinase C activity by staurosporine on estradiol secretion by Sertoli cells isolated from 8–10 days old rats. Staurosporine lead to a dose-related increase in estradiol secretion independent of FSH, such that with 100 nmol/l staurosporine basal estradiol levels increased 10-fold. The maximal response seen with staurosporine alone (100 nmol/l) or in combination with FSH (0.4–8 IU/l) was similar to that seen with a saturating dose of FSH (8 IU/l). There was no evidence of synergy between FSH and staurosporine. Activation of protein kinase C by phorbol 12,13 dibutyrate (10<jats:sup>−7</jats:sup> mol/l) resulted in a 53–74% inhibition of estradiol production provoked by FSH (8 IU/l), staurosporine (5–100 nmol/l) or staurosporine in combination with FSH. Staurosporine (5–100 nmol/l), in the absence or presence of FSH, was unable to overcome inhibition of estradiol secretion by phorbol ester, indicating the presence of at least two independent binding sites on protein kinase C for these molecules. Forskolin (1 μmol/l)- and dibutyryl cAMP (1 mmol/l)-stimulated estradiol secretion was inhibited by 31±5% and 64±5% respectively, by phorbol 12,13 dibutyrate (10<jats:sup>−7</jats:sup> mol/l). We conclude that FSH-induced estradiol secretion in immature rat Sertoli cells is affected by protein kinase C activity.</jats:p>