Evidence that Nitroprusside Stimulates Glucose Uptake in Isolated Rat Cardiomyocytes via Mitogen-activated Protein Kinase

Abstract

Sodium nitroprusside (SNP), a nitric oxide (NO·) donor, stimulates glucose uptake in skeletal muscle. We investigated the stimulatory effect of SNP on glucose uptake in cardiomyocytes and the possible role of soluble guanylate cyclase, phosphatidylinositol-3-kinase (PI-3-kinase) and the mitogen-activated protein kinases (MAPKs). Cardiomyocytes were isolated from adult male Wistar rats by trypsin/collagenase perfusion and glucose uptake determined from the accumulation of 3 H-2-deoxyglucose. SNP caused a dose-dependent increase in glucose uptake with 200-300% increase at 30 mM. Cytochalasin B completely prevented the SNP-induced increase in glucose uptake. 8-Br-cGMP (100µM) and the NO· donor spermineNONOate (100µM) were without effect on basal glucose uptake. SNP-stimulated glucose uptake was not inhibited by the guanylate cyclase inhibitor ODQ (10µM). Sodium ferrocyanide (Na 4 Fe(CN) 6), a compound structurally related to SNP, but without any NO· group, also stimulated glucose uptake in cardiomyocytes suggesting that the effect of SNP could be unrelated to liberation of NO·. Wortmannin, an inhibitor of PI-3-kinase, inhibited insulin-stimulated glucose uptake completely but did not affect SNP-stimulated glucose uptake. SNP-stimulated glucose uptake was inhibited by 50µM PD 098059 (inhibitor of the MAPK-kinases that activate external regulated kinase [ERK1/2]) and by 50µM SB203580 (inhibitor of p38MAPK). In conclusion, high SNP concentrations dose-dependently stimulate glucose uptake in cardiomyocytes and our data suggest a role for MAPK signalling, but not PI-3-kinase and soluble guanylate cyclase, in stimulation of glucose uptake.