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Acceleration of Sugar Transport in Avian Erythrocytes by Catecholamines

From the ¹ From the Department of Physiology, The Milton S. Hershey Medical Center, The Pennsylvania State University, Hershey, Pennsylvania 17033

Epinephrine accelerated the carrier-mediated transport of 3-O-methylglucose and galactose into avian erythrocytes. The magnitude of the effect was dependent upon the period of exposure and the concentration of epinephrine. With 0.1 mm epinephrine, 45 min were required for a significant increase in rate. After 60 min of exposure, a maximal effect was obtained with 0.4 mm epinephrine. Catechol, dopamine, norepinephrine, dl-isoproterenol, and ephedrine also increased transport rate. The stimulatory effect of epinephrine was partially blocked by desmethylimipramine and omission of extracellular potassium, but was unaffected by iproniazid (10 mm), ß-thujaplicin (0.2 mm), propranolol (0.1 mm), or phentolamine (0.1 mm). Addition of a higher concentration (1 mm) of propranolol accelerated 3-O-methylglucose transport. Cyclic adenosine 3' : 5'-monophosphate or its dibutyryl derivative did not increase transport rate when added to the incubation medium. Addition of 1 mm propranolol lowered levels of cyclic adenosine 3' : 5'-monophosphate in control and epinephrine-treated cells, but stimulated the control rate of sugar entry. In contrast to the stimulatory effects on transport of nonmetabolized sugars, epinephrine was ineffective in accelerating glucose uptake. Incubation of avian erythrocytes in buffer containing epinephrine, but not glucose, led to more rapid consumption of ATP, while inclusion of glucose maintained ATP levels either in the presence or absence of the catecholamine. These studies indicate that the acceleration of sugar transport in avian erythrocytes by epinephrine may be related to depletion of cellular ATP.

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