Role of endothelin receptors and relationship with nitric oxide synthase in impaired erectile response in diabetic rats

To evaluate the protective role of bosentan (BOS), an endothelin‐1 (ET‐1) receptor antagonist, and to show the changes in rats with experimentally induced diabetic erectile dysfunction (ED), a total of 24 albino Wistar rats were allocated into four groups. Group 1 was the healthy group and Group 2 had diabetes mellitus (DM) induced by intraperitoneal injection of 60 mg kg^?1 streptozotocin (STZ). Following the establishment of DM, Group 3 and Group 4 were treated with oral BOS doses of 50 mg kg^?1 and 100 mg kg^?1, respectively, for 60 days. At the end of the treatment, we evaluated yawning and erection response to apomorphine treatment and then the animals were sacrificed. ET‐1, eNOS, iNOS, tumour necrosis factor (TNF)‐α, ET‐RA and ET‐RB mRNA expressions were analysed in cavernosal tissue. It was observed that yawning and erection response decreased in the diabetic group; however, both of these improved with BOS treatment. While ET‐1, TNF‐α and iNOS gene expressions increased, eNOS, ET‐RA and ET‐RB gene expressions decreased in the DM group compared to the healthy group. DM has a negative impact on cavernosal tissue blood flow through activating vasoconstrictor mediators in cavernosal tissue. BOS regulates significantly eNOS, iNOS and TNF‐α expressions in a dose‐dependent manner.