The Relaxation Effects of Cynomorii herba in Isolated Corpus Cavernosum Tissues

Abstract

Objective: This study aimed to examine the relaxation effects and underlying mechanisms of Cynomorii herba (CH) extract in isolated rabbit corpus cavernous tissues. Methods: We experimented with CH extract (0.01-3.0 mg/mL). Nω-nitro-L-arginine (L-NNA) was experimented before the CH extract to contracted strips induced by phenylephrine (PE, 1 μM)and compared with nonexperimented. In addition, we experimented with calcium chloride (Ca2+, 1 mM) after pretreatment of the CH extract in Ca2+-free Krebs-Ringer solution to contracted strips induced by PE. The cell viability and nitric oxide (NO) concentration of human umbilical vein endothelial cells (HUVECs) were measured by an methylthiazol-2-yl-2, 5-diphenyl tetrazoliumbromide (MTT) assay and Griess reagent system. The ratio of smooth muscles to collagen fibers, in addition to eNOS- and PDE-5-positive reactions, was examined by histochemical and immunohistochemical staining. Results: The CH extract significantly induced the relaxation of the cavernous strips, and the pretreatment with L-NNA inhibited CH extract-induced relaxation. The L-NNA pretreatment reduced the increased contraction induced by the addition of Ca2+in Ca2+-free solution. Furthermore, the NO concentration of the HUVECs increased. When the CH extract was applied to the corpus cavernosum of the penis (CCP) of Sprague Dawley rats, the ratio of smooth muscles to collagen fibers by PE and the formation of eNOS around the helicine artery increased. However, the CH extract treatment decreased PDE-5 positive reactions. Conclusions: These results show that the relaxation effects induced by the CH extract are associated with the suppression of the influx of extracellular Ca2+ via the production of NO and eNOS and inhibition of PDE-5. Keywords: Cynomorii Herba, corpus cavernosum, NO, eNOS, PDE5