Strain differences in susceptibility to in vivo erectile dysfunction following 6 weeks of induced hyperglycemia in the mouse.

Abstract

INTRODUCTION: With the large-scale availability of transgenic and knockout mouse models, the use of mice may greatly facilitate the examination of the mechanisms underlying diabetic erectile dysfunction (ED). Although in vitro studies of the mouse cavernosum show impairment of vasoreactivity, to date, no studies have demonstrated the in vivo impairment of erectile function in diabetic mice. AIM: To establish whether mouse models of type I diabetes exhibit in vivo ED. METHODS: Hyperglycemia was induced by injection with streptozotocin (STZ, 125 mg/kg x 2 days) in two mouse strains, C57BLKS (BKS) and BALB/c. Six weeks after injection, the cavernosum was removed from some mice for the in vitro assessment of the endothelium and nerve-mediated dilatory responses of the cavernosal strips. The in vivo assessment of intracorporal pressure normalized to mean arterial pressure, in response to the electrical stimulation of the cavernosal nerve, was performed in the remaining mice. MAIN OUTCOME MEASURES: The main outcome measure of this study was the in vivo assessment of erectile function following diabetic induction in mice. RESULTS: Despite similar levels of sustained hyperglycemia following STZ injection, the phenotype of diabetic ED was observed only in BKS and not BALB/c mice. The cavernosum from diabetic BKS mice showed decreased endothelium-dependent dilation in response to acetylcholine (ACh), as well as impaired parasympathetic nerve-mediated relaxation. There was no change in ACh or nerve-mediated relaxation in the cavernousum from diabetic vs. control BALB/c mice. Further, in vivo physiologic assessment of erectile activity revealed a significant decrease in erectile function in diabetic BKS but not in BALB/c mice. CONCLUSION: Together these data first established in vivo ED in a mouse model of type I diabetes (BKS mouse) and importantly demonstrated that certain inbred strains may be protected from hyperglycemia-induced erectile impairment. Further study of the strain-dependent effects may offer important clues into the mechanisms of ED as it relates to type I diabetes.