The relaxant effect of ginseng saponin on the bladder and prostatic urethra: an in vitro and in vivo study.

AIM: To assess the effects of ginseng saponin on relaxation of the bladder and prostatic urethra and to determine its mechanism of action. MATERIALS AND METHODS: For the in vitro study, prostatic urethra muscle strips were harvested from 18 male New Zealand rabbits. The strips were mounted in organ baths and connected to force displacement transducers. After stabilization, maximal tissue contractions were obtained by the application of phenylepinephrine to the urethra strips, and a dose-response curve for ginseng saponin was constructed (10(-6)-10(-2)M). After pretreatment of urethra strips with N-nitro-L-arginine methyl ester (L-NAME), another dose-response curve for ginseng saponin was constructed. For the in vivo study, we used adult male Sprague-Dawley rats divided into three groups [control, partial bladder outlet obstruction (PBOO) and saponin-fed groups], and we monitored the vesical pressure (P(ves)) and urethral perfusion pressure (UPP). RESULTS: The ginseng saponin induced a significant dose-dependent relaxant effect on the prostatic urethra strips. A significant relaxant effect of ginseng saponin was observed from 10(-3)M, and ginseng saponin significantly relaxed urethra strips by 50.2 ± 20.26% at 10(-2)M. The relaxant effect was partially inhibited with L-NAME pretreatment. In the in vivo study, the change in UPP between baseline and relaxation was significantly higher in the saponin group than in the control or PBOO group (p < 0.001). The saponin group showed a significantly lower baseline P(ves) than the PBOO group. CONCLUSIONS: We observed a significant relaxation effect of ginseng saponin on the bladder and prostatic urethra in both in vitro and in vivo studies. The mechanism by which ginseng saponin induces relaxation appears to involve the nitric oxide/nitric oxide synthase pathway.

Silencing of the GnRH type 1 receptor blocks the antiproliferative effect of the GnRH agonist, leuprolide, on the androgen-independent prostate cancer cell line DU145.

This study investigated the mechanism of action of a gonadotropin-releasing hormone (GnRH) agonist, leuprolide, on proliferation of the hormone-refractory prostate cancer cell line DU145, transfected with short hairpin RNA (shRNA), to reduce expression of the GNRHR1 gene (which encodes the GnRH type 1 receptor). DU145 cell proliferation in the presence of leuprolide (10(-9) and 10(-7) M) or control medium was measured before and after GnRHR1 knockdown. Reverse transcription-polymerase chain reaction and Western blot analysis were used to measure the degree of GNRHR1 silencing. DU145 cells treated with leuprolide (10(-9) and 10(-7) M) showed significant growth inhibition compared with control-treated DU145 cells. Transfection with GNRHR1 -shRNA significantly decreased GNRHR1 expression at 48 h. DU145 cells transfected with silencing GNRHR1 -shRNA showed normal growth patterns; however, there was no significant inhibition of proliferation of DU145 cells transfected with GNRHR1 -shRNA compared with cells transfected with control-shRNA in response to leuprolide. These data demonstrated that the antiproliferative effect of leuprolide was mediated by the GnRHR1.