Lowering of kininogen in rat blood by adrenaline and its inhibition by sympatholytic agents, heparin and aspirin.

1 (-)-Adrenaline lowered the kininogen content and transitorily elevated the fibrinolytic activity of plasma following intravenous injection into the rat. Its effect on kininogen increased when administered by intravenous infusion.2 Although less effective, (-)-noradrenaline had a similar action to adrenaline; (+/-)-isoprenaline was inactive and failed to inhibit the effect of adrenaline.3 The effect of adrenaline on kininogen could be reproduced in vitro by incubation of whole blood, but not cell-free plasma, with the catecholamine for 5 min at 37 degrees C.4 Propranolol or phenoxybenzamine, as well as heparin or acetylsalicylic acid (aspirin), blocked the reduction of rat blood kininogen by adrenaline in vivo and in vitro.