Phorbol ester-induced contractility and Ca2+ influx in human cultured prostatic stromal cells

In this study, we investigated the effects of protein kinase C (PKC)-activating phorbol esters upon Ca(2+) influx and contractility in human cultured prostatic stromal cells. Tissue obtained from patients undergoing transurethral resection of the prostate was used to generate explant cultures of prostatic stromal cells. These cells expressed detectable levels of PKCalpha, delta, gamma, lambda, and zeta, but not epsilon, iota, mu, or theta; isoforms and responded to both phorbol 12,13-diacetate (PDA) and 12-deoxyphorbol 13-tetradecanoate (DPT) with concentration-dependent contractions (pEC50+/-SEM 7.07+/-0.41 and 6.39+/-0.27, respectively). The L-type Ca2+ channel blocker nifedipine (3 microM), and the PKC inhibitors G? 6976, G? 6983 (both 100 nM), myristoylated PKC inhibitor 19-27 (20 microM) and bisindolylmaleimide (1 microM) all abolished PDA-stimulated (1 microM) contractions. Neither PDA nor DPT (at 1 microM) caused translocation of any PKC isoform from the cytosolic to the particulate fraction. Nifedipine (3 microM), myristoylated PKC inhibitor 19-27 (20 microM), and bisindolylmaleimide (1 microM) inhibited PDA-stimulated Ca2+ influx into FURA-2 loaded cells. This study indicates that human cultured prostatic stromal cells respond to phorbol esters with contractions that are dependent upon the influx of Ca2+ through L-type Ca2+ channels and that this effect may be independent of the translocation of PKC from cytosolic to particulate fractions.