Mechanisms of action of hypocapnic alkalosis on limb blood vessels in man and dog.

KONTOS, HERMES A., DAVID W RICHARDSON, A. JARRELL RAPER, ZUBAIR-UL-HASSAN, AND JOHN L. PATTERSON, JR. Mechanisms of action of hypocapnic alkalosis on limb blood vessels in man and dog. Am. J. Physiol. 223(6) : 1296-1307. 1972.-The mechanisms of action of hypocapnic alkalosis on limb blood vessels were investigated in man and in the anesthetized dog. In man hypocapnic alkalosis was produced by voluntary hyperventilation or by intraarterial administration of tromethamine, and in the dog it was produced by intra-arterial administration of tromethamine or sodium hydroxide. Hypocapnic alkalosis had a biphasic effect on limb blood vessels consisting of an initial vasodilator effect and a subsequent vasoconstrictor action, The initial vasodilation was primarily related to release of histamine, since it was accompanied by increased blood histamine concentration and since it was inhibited or reversed by antihistamines. The subsequent vasoconstriction probably represented the direct action of hypocapnic alkalosis on vascular smooth muscle. Other mechanisms, such as changes in the activity of vasomotor nerves, release of catecholamines, and changes in calcium ion activity were found to play no significant role in the response of limb blood vessels to hypocapnic alkalosis.