Calcium/phospholipid-dependent protein kinases in rat Sertoli cells: Regulation of androgen receptor messenger ribonucleic acid

The possibility that Sertoli cell responses to testosterone are modulated b y the calcium/phospholipid-dependent protein kinase (protein kinase C; PKC) was examined in rat Sertoli cells in culture. Both soluble and particulate cell fractions showed low constitutive phosphotransferase activity. Incuba tion with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA; 10(- 7) M) was associated with a transient induction in both cell fractions of c alcium/phosphatidylserine-dependent PKC activity; which was elevated from 1 5 min to 1 h. Consistent with this, mRNAs for the calcium/phospholipid-depe ndent isomeric forms of PKC (alpha, beta, and gamma) were detected. The exp ression levels of mRNAs for PKC alpha and PKC beta were also up-regulated ( 2.5- to 3-fold) by TPA (10-7 M), but these effects were much slower (peakin g after 12 h) than those on phosphotransferase activity. In the presence of TPA (10-7 M), expression of androgen receptor (AR) mRNA showed a transient time-dependent down-regulation (similar to 70%), in which the nadir was re ached after 6 h and baseline expression was again obtained after 12 h. The regulatory, effect of PKC activation on AR mRNA was confirmed by the absenc e of response to a biologically inactive phorbol ester, A concentration-dep endent decrease (half-maximal effect at similar to 10(-8) hi TPA) of AR mRN A was also observed. These data suggest that Sertoli cell responses to test osterone may be inhibited by a transiently active PKC with a wide intracell ular distribution.