THE EFFECT OF ACETYLCHOLINE ON THE HUMAN PULMONARY CIRCULATION UNDER NORMAL AND HYPOXIC CONDITIONS1

Abstract

It is generally accepted that the tone of the peripheral arterioles plays an important part in regulating the systemic blood pressure in man. Whether the small vessels of the lungs exercise similar control over the pressure in the pulmonary artery is not so certain. This uncertainty has stemmed largely from the fact that the human pul- monary vessels have exhibited an erratic response to many vasoactive drugs (1-15). As a conse- quence, most physiologists have concluded either that the pulmonary vessels are incapable of in- trinsic changes in tone, or that the effect of such changes, if they occur, is less important in deter- mining the pulmonary arterial pressure than is the effect of mechanical factors alone.