[Age and the effect of noradrenaline on the physiologic properties and cyclic 3',5'-adenosine monophosphate content of portal vein smooth muscle cells].

With ageing, the threshold doses of noradrenaline necessary for initial electric and contractile responses of the vessel smooth muscle cells, significantly decrease. The levels of cyclic 3'5' adenosinmonophosphorous acid (cAMP) in the portal vein's walls differ insignificantly in adult and old animals. The noradrenaline effect on the portal vein of old animals involves a more obvious increase in the cAMP content. The increased sensitivity of the vessel smooth muscle cells to noradrenaline in old animals seems to be due to the fact that in old animals the adenylatcyclase -- cAMP system responds to lesser amounts of noradrenaline.