Alpha 2-adrenoceptor stimulation affects total glucose utilization in isolated islets of Langerhans

SG Laychock

Glucose utilization in isolated islets of Langerhans of the rat was determined by measuring the conversion of [5-3H]glucose (10 mM) to 3H2O. The alpha 2-adrenoceptor agonists clonidine, epinephrine, and norepinephrine in the presence of the alpha 1-adrenoceptor antagonist prazosin and the beta-adrenoceptor antagonist propranolol inhibited glucose utilization by as much as 50%. Yohimbine, an alpha 2- adrenoceptor antagonist, reversed the reduction in glucose utilization evoked by alpha 2 receptor agonists. The cholinomimetics carbachol and muscarine, and 8-bromo-cyclic GMP, but not other cyclic nucleotides, reversed the clonidine-induced suppression of glucose utilization. 3- Isobutyl-1-methylxanthine potentiated the stimulation of glucose utilization by carbachol with clonidine. In contrast, the beta- adrenoceptor agonist isoproterenol did not affect glucose utilization. Forskolin, which activates adenylate cyclase, reduced glucose utilization and did not affect the inhibitory response to clonidine. The ester phorbol 12,13-dibutyrate induced a latent reversal of the effects of clonidine. Insulin release paralleled changes in glucose utilization with alpha 2-adrenoceptor agonists. Carbachol and 8-bromo- cyclic GMP antagonized the alpha 2-adrenoceptor-induced inhibition of insulin release. During sustained insulin release (60 min), 8-bromo- cyclic AMP became a more potent modulator of secretion than 8-bromo- cyclic GMP in the presence of clonidine, although glucose utilization was not enhanced by 8-bromo-cyclic AMP.

Volume 32, Issue 1, pp. 241-248, 08/01/1987
Copyright © 1987 by American Society for Pharmacology and Experimental Therapeutics

This article has been cited by other articles:

				M. Srinivasan, R. Aalinkeel, F. Song, B. Lee, S. G. Laychock, and M. S. Patel Adaptive changes in insulin secretion by islets from neonatal rats raised on a high-carbohydrate formula Am J Physiol Endocrinol Metab, December 1, 2000; 279(6): E1347 - E1357. [Abstract] [Full Text] [PDF]