Role of Paricalcitrol as an Active Vitamin D Analogue on Erectile Function and Penile NOS Expression in Diabetic Rats

Abstract

Objectives: To investigate the effect of paricalcitrol as a vitamin D analogue on erectile dysfunction and on the penile expression of superoxide anion generationand nitric oxide synthase (NOS) isoforms instreptozotocin-induced diabetic rats models. Methods: Male Sprague-Dawley rats were used in this study. Diabetes was induced by a one-time intraperitoneal injection of streptozotocin (60 mg/kg). The rats with blood glucose levels above 300 mg/dL were selected for the study. The erectile function of the rats was assessed by recording frequency of erection after subcutaneous injection of apomorphine (80 ug/kg). Those were divided into 2 groups (N = 10 per group): i) EDDM (erectile dysfunction diabetes mellitus) group fed with saline and ii) EDDM + paricalcitrol treated group receiving paricalcitrol (0.4 µg/k/day) by intraperitoneal injection. 10 animals were used as a control group and received no streptozotocin. 4 weeks later, the erectile function of the rats was assessed by recording frequency of erection after subcutaneous injection of apomorphine (80 ug/kg). Superoxide anion generation and mRNA expression of of nNOS and eNOS were evaluated in corpora cavernosum tissue. Results: Penile erection, the expression of both nNOS, eNOS generation was significantly elevated however the superoxide generation was significantly decreased in paricalcitrol treated group compared to diabetic group. Conclusion: Treatment with paricalcitrol for 4 weeks improves erectile dysfunction in diabetic rats probably by improving expression of nitric oxide synthase expression and decreasing superoxide production.