Effects of Pygeum africanum extract (Tadenan (R)) on vasoactive intestinalpeptide receptors, G proteins, and adenylyl cyclase in rat ventral prostate

BACKGROUND. Tadenan(R) (a Pygeum africanum extract) is a drug used in the t reatment of benign prostatic hyperplasia. Its effects on prostate fibroblas t proliferation and bladder function after partial outlet obstruction have been demonstrated in various pharmacological studies. However, its effects at the molecular level are poorly documented. METHODS. Tadenan(R) was dissolved in peanut oil. Rats were orally given two daily doses of the drug (1 or 10 mg/kg b.w.) for 4 days. Vasoactive intest inal peptide (VIP) binding, adenylyl cyclase stimulation, and expression of G-protein subunits were studied in rat prostatic membranes by established procedures. RESULTS. Tadenan(R) treatment of castrated/testosterone-replaced rats was p erformed in order to interfere with prostatic cell proliferation. This expe rimental approach resulted in increases of: 1) VIP effect on adenylyl cycla se stimulation through alpha (s) G-subunit; 2) alpha (i) activation by low Gpp[NH]p doses tin the presence of forskolin); and 3) alpha (s), alpha (i1/ 2), and alpha (i3/0), levels. However, there were no modifications in membr anes from quiescent, nonproliferating prostates (untreated rats). CONCLUSIONS. The observed regulatory role of Tadenan(R) on various prostati c components of the adenylyl cyclase system, together with previous finding s on protein kinase C-mediated signal transduction, open a complex array of possibilities of direct actions of this phytotherapeutic agent in the pros tate. Prostate 45:245-252, 2000. (C) 2000 Wiley-Liss, Inc.