Vanadyl and vanadate inhibit Ca2+ transport systems of the adipocyte plasma membrane and endoplasmic reticulum.
Vanadate and vanadyl have many insulin-mimetic effects on cellular metabolism and also have been shown to alter cellular Ca2+ fluxes. In this report, vanadate and vanadyl, like insulin, are shown to inhibit the plasma membrane (Ca2+ + Mg2+)-ATPase/Ca2+ transport system as well as Ca2+ transport by endoplasmic reticulum from rat adipocytes. Ca2+ transport by the endoplasmic reticulum was inhibited half-maximally (I50) by vanadate and vanadyl at concentrations of 30 and 33 microM, respectively. Inhibition of the plasma membrane Ca2+ transport by vanadate and vanadyl was less sensitive, with I50 values of 144 and 92 microM, respectively. These I50 values for plasma membrane Ca2+ transport were similar when measured under conditions of calmodulin-stimulated and non-calmodulin-stimulated Ca2+ transport. The predominant effect of both ions on the kinetic parameters of Ca2+ transport was a substantial decrease in the Vmax by 43-46% for both transport systems. An increase in intracellular Ca2+ following the inhibition of the (Ca2+ + Mg2+)-ATPase/Ca2+ pump in the plasma membrane and endoplasmic reticulum by these vanadium ions may result, at least in part, in the observed insulin-mimetic alterations in cellular metabolism.
Delfert
D M
DM
McDonald
J M
JM
D000273:Adipose Tissue / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D017301:Ca(2+) Mg(2+)-ATPase; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology*
D014639:Vanadium; D014638:Vanadates; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium