The effects of vanadate on calcium transport in dialyzed squid axons. Sidedness of vanadate-cation interactions.
(1) Vanadate (VO3-) fully inhibits the ATP-dependent uncoupled Ca efflux (Ca pump) in dialyzed squid axons. (2) Vanadate inhibits with high affinity. The mean apparent affinity (K 1/2) obtained was 7 microM. (3) Inhibition by vanadate is dependent on Cao. External Ca lead to a release of the inhibitory effect. (K 1/2 congruent to 3 mM). This antagonistic effect can be reverted by increasing the vanadate concentration. Internal K+ increases the affinity of the intracellular vanadate binding site. External K+ has no effect on the inhibition. (4) Vanadate has no effect on the Nao-dependent Ca efflux component (forward Na-Ca exchange) in the absence of ATP. In axons containing ATP vanadate modified this component.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001369:Axons / Q000378:metabolism*; D001665:Binding Sites; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D049832:Decapodiformes; D003956:Dialysis; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology*
D014639:Vanadium; D014638:Vanadates; D000255:Adenosine Triphosphate; D012964:Sodium; D011188:Potassium; D002118:Calcium