The present study was aimed at investigating the effects of diabetes on the cavernosal smooth muscle relaxations mediated by adenosine and adenosine triphosphate (ATP) in tissues obtained from men and rats. Adenosine- and ATP-induced relaxant responses showed an enhanced sensitivity with an unaltered effectiveness in diabetic men. Adenosine-elicited relaxation in diabetic rat corporeal tissues exhibited enhanced effectiveness with unaltered sensitivity, whereas ATP-induced relaxations were decreased in diabetic animals when compared to control animals. Tetraethylammonium pretreatment, but not glibenclamide, L-NAME and 8-phenyltheophylline, normalized enhanced apparent affinity to adenosine in tissue from diabetic men and effectiveness (E(max)) to adenosine in diabetic rats. These results suggest that adenosine-elicited relaxation in diabetes is controlled at the receptor level events including K(+) channels in men whereas in rats postreceptor-related events including K(+) channels control the adenosine-induced relaxation. These relaxations to adenosine and ATP in men and rats with and without diabetes may be nitric oxide-independent mechanisms. Our results also suggest that ATP-induced relaxation did not involve K(ATP) channels and Ca-activated K(+) channels.
Copyright 2000 S. Karger AG, Basel