Influence of chronic ethanol consumption on arterial tone in young and aged rats

The aim of this work was to evaluate the effects of long-term ethanol consu mption on arterial responses in vitro in young and aged rats. Therefore, Wi star rats (ages 3 and 29 mo, respectively) were allocated to six groups: co ntrol-young, sucrose-young, ethanol-young, control-aged, sucrose-aged, and ethanol-aged. The ethanol-fed groups were given 25% ethanol by intragastric gavage three times a day 4 days a week. Responses of mesenteric arterial r ings were examined in standard organ chambers after 5 treatment weeks. In n orepinephrine-precontracted arterial rings, endothelium-dependent relaxatio ns to acetylcholine, as well as endothelium-independent relaxations to isop roterenol, were attenuated in aged rats when compared with young controls. Relaxation responses to isoproterenol, but not to acetylcholine and nitropr usside, were clearly improved by ethanol treatment in both young and aged r ats. The cyclooxygenase inhibitor diclofenac, which reduces the synthesis o f dilating and constricting prostanoids, enhanced the relaxation to acetylc holine in all three aged rat groups but was without significant effect in t he young rats. In the presence of the nitric oxide synthase inhibitor N-G-n itro-L-arginine methyl ester the relaxation to acetylcholine in control and sucrose-fed aged rats was markedly reduced compared with control rats, whe reas in the young controls and in both young and aged ethanol-exposed group s, distinct relaxations to higher concentrations of acetylcholine were stil l present. The endothelium-independent relaxations to cromakalim, a hyperpo larizing vasodilator acting via ATP-sensitive potassium channels, were also markedly augmented by ethanol feeding in both young and aged rats. In conc lusion, ethanol consumption in both young and aged rats was associated with markedly improved arterial relaxations to isoproterenol and cromakalim, as well as clearly augmented relaxation to acetylcholine during inhibition of cyclooxygenase and nitric oxide synthase. These findings suggest that espe cially the potassium channel-related component of arterial relaxation was a ugmented by long-term ethanol exposure.