Relationship between the Metabolic and Vasodilator Effects of Epinephrine in Human Forearm Muscle

Abstract

The effect of intra-arterial and intravenous epinephrine on skeletal muscle blood flow and metabolism were studied in the human forearm following complete suppression of the circulation to forearm skin by epinephrine inotophoresis. Epinephrine by either route of administration increased blood flow, O 2 consumption and CO 2 production, and decreased arteriovenous differences of O 2 and CO 2 across the forearm. The increments in blood flow did not correlate with the increments in O 2 consumption or CO 2 production. In the intact forearm intravenous epinephrine increased deep forearm venous Po 2 but not venous PCo 2 . Hypocapnia, induced by voluntary hyperventilation, did not alter the response of forearm blood flow to intravenous epinephrine. These results show that the vasodilator response of skeletal muscle vessels to epinephrine is not dependent on decrease in Po 2 or increase in PCO 2 in the environment of the high resistance vessels. They also suggest that the calorigenic effect of the hormone is not a dominant factor in its vasodilator effect in skeletal muscle.