The contractile RhoA/Rho-kinase (Rock) signalling pathway is up-regulated in penile tissue in animal models of experimental diabetes and has been proposed to contribute to diabetes-related erectile dysfunction (ED). In previous studies we demonstrated that testosterone (T) restores diabetes-induced ED by influencing the NO/cGMP/PDE5 pathway.AimTo investigate the effect of T on the RhoA/Rock signalling in course of diabetes.MethodsWe used two distinct animal models of chemical diabetes (alloxan-induced in the rabbit and streptozotocin-induced in the rat) with or not T supplementation.ResultsIn both models, hypogonadism was observed, characterized by reduced T plasma level and androgen-dependent accessory glands atrophy. Diabetic animals showed a significant increase in responsiveness to increasing concentrations of Y-27632, a highly selective Rock inhibitor, as evaluated either by in vitro contractility study (diabetic-rabbit) and in vivo as erectile response elicited by intracavernous injections (diabetic-rats). T-substitution (30 mg/kg, weekly) completely reverted hypogonadism and diabetes-induced penile hypersensitivity to Y-27632. To test whether this effect was due to a T-dependent regulation of RhoA/Rock gene expression, we measured RhoA/Rock mRNA. Both isoforms of Rock (Rock1/Rock2) were analyzed by real time RT-PCR in rat penile samples. We found that Rock1 mRNA was significantly increased (P<0.05) in penile tissues from diabetic animals and restored to the control values by T, as also confirmed by semiquantitative RT-PCR in rabbit. Conversely, RhoA and Rock2 mRNA expression was not influenced neither by diabetic condition and by T administration. Accordingly, Rock1 protein expression, as evaluated by western blot and immunohistochemistry analysis, resulted increased in penile samples from diabetic animals and normalized by T.ConclusionsOur data further support the hypothesis that the activation of RhoA/Rock signalling contributes to diabetes-related erectile dysfunction. Moreover, treating hypogonadism in course of diabetes, may restore erectile function also by normalizing RhoA/ Rock pathway over-activity.