Relaxing Mechanism of Gami-Shinkiwhan in Corpus Cavernosum Smooth Muscle

Objectives: The purpose of this study was to investigate the relaxation effects and mechanisms of Gami-Shinkiwhan (GS) in corpus cavernosum smooth muscle. Methods/Statistical Analysis: We treated isolated corpus cavernous strips with the water extract of GS and also with 1 mm of calcium chloride (Ca2+), after pretreatment with GS in a Ca2+-free Krebs-Ringer solution. Contraction strips were pretreated with Nω-nitro-L-arginine (L-NNA) before GS. Nitric oxide (NO) concentration in human umbilical vein endothelial cells (HUVECs) was measured by Griess reagent. Endothelial NO syntheses (eNOS) and phosphodiesterase5 (PDE5) production was investigated by histochemical and immunohistochemical staining. Findings: GS significantly affected the relaxation of cavernous strips. GS-induced relaxation was inhibited by pretreatment with L-NNA. Contraction induced by the addition of Ca2+ was decreased by treatment with the GS extract, compared to the non-treatment with the GS extract in Ca2+-free solution. NO concentration in HUVECs was increased by pretreatment of GS. When GS was applied to the corpus cavernosum penis of rats, the ratio of smooth muscles to collagen fibers decreased. The formation of eNOS around the corpus cavernosum smooth muscle increased but PDE5 formation decreased. Improvements/Applications: The smooth muscle relaxation effects of GS on the corpus cavernosum is regulated by suppressing the influx of extracellular Ca2+ through the production of NO and suppression of PDE5.