Hyperactivity of Ca channels in vasa deferentia smooth muscle of diabetic rats

Contractile responses of strips of the prostatic end of vasa deferentia isolated from streptozotocin-treated diabetic rats were investigated with five agonists. Agonists induced similar biphasic responses in vasa deferentia from diabetic and age-matched control rats six to seven weeks after streptozotocin. Twitches were observed superimposed on contractions induced by the adrenergic agonists in strips from most of the diabetic rats. Strips from the diabetic rats developed significantly greater tension than those from the controls. Especially, strips from diabetics had remarkably greater dose-related responses to Ca, and greater Ca influx, than controls when tested in the presence of either KCl or clonidine. The results suggest that both voltage-dependent Ca channels and receptor-operated Ca channels contribute to potentiation of contractile responses in diabetes.