Effects of aging on ATP sensitive K+ channels and on prostanoid productionin 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 sens itive K+ channels functionality. Moreover, studies were performed in order to evaluate the effects of aging on the synthesis of Vascular prostanoids a s well as on its possible contribution to the presser responses of this vas cular bed. Male Wistar rats of 3 month (adults) and 24 month (aged) were us ed. Although no differences were found among adult and aged rats in presser responses to 2-30 nmol noradrenaline and to 40-160 nmol KCI, 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, wh ereas PGF(2)alpha and 6-keto PGF(1)alpha production was not modified with a ge, the thromboxane B-2 and prostaglandin E-2 production in the mesenteric bed from 24 month old rats was significantly increased compared to the adul t group. Furthermore, the cyclooxigenase synthesis inhibitor, 10(-5) M indo methacin reduced the presser responses induced by noradrenaline in the mese nteric 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+ ch annels in the rat mesenteric bed. In addition, aging produces an increase i n the release of Vasoconstrictor as well as of vasodilator prostanoids, who se contribution to noradrenaline induced pressor responses appears to be le ss relevant in the older animals.