Effects of Epinephrine on Forearm Blood Flow and Metabolism in Man *

Abstract

Continuous intra-arterial infusion of epinephrine for a sufficiently long period and in concentrations that were probably within the range of those achieved endogenously in response to a number of normal stimuli caused: immediate and sustained increase in blood flow; glycogenolysis as demonstrated by marked net output of lactic acid from deep forearm tissues in excess of glucose uptake; no significant change in glucose uptake by deep forearm tissues; potassium uptake, clearly not secondary to glucose uptake or to endogenous insulin release; and, output of free fatty acids from superficial and deep forearm adipose tissue. Continuous intravenous infusion of epinephrine at the same rate as that given intra-arterially had no effect on forearm blood flow or metabolism. Continuous intra-arterial infusion of epinephrine at a rate 3 to 10 times that used in experiments summarized above caused only transient increase in blood flow followed by either prolonged reduction or no net change in blood flow. However, metabolic effects of the larger rate of infusion of epinephrine were similar to those of the smaller rate of infusion. In particular, venous lactate concentrations were even greater than in those experiments in which net vasodilatation occurred. It is, therefore, difficult to attribute the vasodilating response to epinephrine as secondary to increased lactate concentration.