Alpha-1 Adrenergic Stimulation of Glucose Uptake in Rat White Adipocytes1

Abstract

We recently demonstrated that adipocyte lactate production depends onalpha-1 adrenergic control and that adipocytes can produce lactate even when insulin-stimulated glucose uptake is markedly impaired. This prompted us to investigate the glucose uptake in response to an alpha-1 adrenergic stimulation. We measured the adrenergic regulation of glucose uptake by adipocytes isolated from epididymal white adipose tissue using agonists (norepinephrine, phenylephrine and isoproterenol) and antagonists (prazosin and propranolol) of alpha-1 andbeta adrenoceptor subtypes. Our results show that the maximal glucose uptake obtained in the presence of 10⁻⁸ M norepinephrine is partially inhibited by prazosin (10⁻⁶ M, 57%) or propranolol (10⁻⁶ M, 52%) suggesting that glucose uptake is subjected to both alpha-1 and betaregulation. Indeed, our findings show that glucose uptake is dose-dependently increased by phenylephrine. This stimulation is totally inhibited by prazosin (10⁻⁶ M). Isoproterenol stimulated glucose uptake. The stimulation of glucose uptake by isoproterenol is totally inhibited in the presence of propranolol (10⁻⁶ M) in the incubation medium. Our results demonstrate for the first time that alpha-1 adrenergic subtype is involved in the regulation of glucose uptake by white adipocytes.