An Insulin-induced, Endothelium-dependent Relaxation Mechanism of Normal Rabbit Cavernous Smooth Muscle / 대한비뇨기과학회지

ABSTRACT

Purpose: Insulin is known to induce relaxation in various vasculatures by increasing the release of nitric oxide or the expression of nitric oxide synthase. However, its action mechanisms on the corpus cavernosum remain to be uncovered. This study aimed to investigate the relaxative responses and the mechanism of normal cavernous smooth muscles to insulin. Methods and Materials: Rabbit corpus cavernous tissues were prepared in 2x2x8 mm sized strip for isotonic tension recording. The dose-dependent relaxation responses of norepinephrine (10(-4)M)-precontracted strips to insulin (10(-6)M)were measured. The relaxation responses of NE (10(-4)M)-precontracted strips to insulin (10(-6)M) were measured under low to high glucose concentrations (0, 0.1, 1 and 11mM) in physiological solution. The relaxation responses of the NE-precontracted strips to insulin (10(-6)M) were also observed after endothelial denudation, 30-minute preincubation with L-NAME (5mM) or 30-minute preincubation with indomethacin (10(-4)M). Results: The cavernosal strips were relaxed by insulin in a dose-dependent manner. The insulin-induced relaxation was dose-dependently increased by glucose. The endothelial denudation or indomethacin pretreatment almost abolished the insulin-induced relaxation, but L-NAME rarely affected the relaxation. Conclusions: Insulin induces an endothelium-dependent relaxation of rabbit cavernous smooth muscles, which is mostly NO-independent, but seems to be related with prostaglandins or their metabolites.