INSULIN-LIKE VS NON-INSULIN-LIKE STIMULATION OF GLUCOSE-METABOLISM BYVANADIUM, TUNGSTEN, AND SELENIUM-COMPOUNDS IN RAT MUSCLE

The direct impact of vanadate, tungstate, selenate, and selenite on gl ucose metabolism of isolated rat soleus muscle was investigated. All c ompounds stimulated glucose transport, but only vanadate exerted an in sulin-like effect on glycogen synthesis (mu mol glucose into glycogen g(-1)h(-1): control, 1.43+/-0.11 vs. 1 mmol/l vanadate, 2.08+/-0.11, p<0.0001), which was more distinct in the presence of 1 mmol/l H2O2 (c ontrol, 1.44+/-0.13 vs. 1 mmol/l vanadate, 3.49+/-0.12, p<0.001). Gluc ose handling of muscles exposed to tungstate, selenate, or selenite re sembled that of hypoxic muscle, i.e. the induced rise in glucose uptak e was inhibited by dantrolene and associated with high rates of glycol ysis and rapid glycogen depletion (glycogen content after incubation, mu mol glucosyl units/g: control, 16.2+/-0.7 vs. hypoxia, 2.7+/-0.5, p <0.0001; control, 17.0+/-0.5 vs. 100 mmol/l tungstate, 5.5+/-0.4, p<0. 001; control, 16.2+/-0.7 vs. 100 mmol/l selenate, 1.5+/-0.3, and vs. 3 00 mu mol/l selenite, 1.7+/-0.3, p<0.0001 each). The results suggest t hat vanadate (and more pronounced it's peroxides) exerts true insulin- like action on isolated muscle glucose metabolism, whereas tungsten an d selenium salts trigger glucose transport in association with a catab olic response, which may represent an unspecific response to toxic/osm otic stress.