INSULIN-LIKE ACTIONS OF VANADATE ARE MEDIATED IN AN INSULIN-RECEPTOR-INDEPENDENT MANNER VIA NONRECEPTOR PROTEIN-TYROSINE KINASES AND PROTEIN PHOSPHOTYROSINE PHOSPHATASES

Most or all mammalian cells contain vanadium at a concentration of 0.1 -1.0 mu M. The bulk of the vanadium in cells is probably in the reduce d vanadyl (IV) form. Although this element is essential and should be present in the diet in minute quantities, no known physiological role for vanadium has been found thus far. In the years 1975-1980 the vanad ate ion was shown to act as an efficient inhibitor of Na+,K+-ATPase an d of other related phosphohydrolyzes as well. In 1980 it was observed that vanadate vanadyl, when added to intact rat adipocytes, mimics the biological actions of insulin in stimulating hexose uptake and glucos e oxidation. This initiated a long, currently active, field of researc h among basic scientists and diabetologists. Several of the aspects st udied are reviewed here.