Effects of aging on ATP sensitive K(+) channels and on prostanoid production in the rat mesenteric bed.

The aim of the present work was to evaluate, in the rat isolated mesenteric bed, whether increasing age is associated with alterations in the ATP sensitive K(+) channels functionality. Moreover, studies were performed in order to evaluate the effects of aging on the synthesis of vascular prostanoids as well as on its possible contribution to the pressor responses of this vascular bed. Male Wistar rats of 3 month (adults) and 24 month (aged) were used. Although no differences were found among adult and aged rats in pressor responses to 2-30 nmol noradrenaline and to 40-160 nmol KCl, the relaxant responses to the K(+) channel opener, 10(-6) M cromakalim, were significantly diminished in the aged group compared to the adults. On the other hand, whereas PGF2α and 6-keto PGF1α production was not modified with age, the thromboxane B2 and prostaglandin E2 production in the mesenteric bed from 24 month old rats was significantly increased compared to the adult group. Furthermore, the cyclooxigenase synthesis inhibitor, 10(-5) M indomethacin reduced the pressor responses induced by noradrenaline in the mesenteric beds from adults but not from aged rats. It is concluded that there is an age related reduction in the functionality of the ATP sensitive K(+) channels in the rat mesenteric bed. In addition, aging produces an increase in the release of vasoconstrictor as well as of vasodilator prostanoids, whose contribution to noradrenaline induced pressor responses appears to be less relevant in the older animals.