Phenylarsine oxide and hydrogen peroxide stimulate glucose transport via different pathways in isolated cardiac myocytes

Abstract

The aim of this study was to investigate the stimulating effects of sulfhydryl reagents on glucose transport in isolated rat heart muscle cells and to compare them with the action of insulin. Low concentrations of the sulfhydryl oxidants hydrogen peroxide (H 2O 2) and diamide (5–100 μM), but also of phenylarsine oxide (PAO) (0.5–3 μM), that is known to specifically react with vicinal SH-groups, stimulated the rate of 2-deoxy- d-glucose uptake by a factor of 4 to 8 in these cells, while higher concentrations were inhibitory. The stimulating effects of H 2O 2 or diamide, and, to a significantly lesser extent, those of PAO or insulin, were depressed in cells pretreated with the sulfhydryl-alkylating agent N-ethylmaleimide (56–100 μM). H 2O 2 raised the V max and lowered the K m of 3-O- methyl- d- glucose uptake, while PAO or insulin solely increased V max. The increase in glucose transport caused by H 2O 2 was antagonized by the β-adrenergic agonist isoprenaline (1 μM) or by a membrane-permeant cyclic AMP analog, whereas the effects of PAO or insulin were not altered. The action of H 2O 2 was additive with the stimulation induced by the protein phosphatase inhibitors okadaic acid (1 μM) or vanadate (6 mM), whereas the responses to PAO or insulin were reduced in the presence of these agents. Finally, H 2O 2 and PAO, but not insulin, acted additively with the protein kinase C ligand phorbol myristate acetate (0.8 μM) and with phospholipase C (0.03 units/ml). We conclude that, in cardiac myocytes, H 2O 2, on the one hand, and PAO (and possibly insulin), on the other hand, stimulate glucose transport via at least two distinct, SH-dependent pathways. These pathways, in turn, differ from a protein kinase C- and from a phospholipase C-mediated mechanism.