title: Calcium ion transport by pig erythrocyte membrane vesicles.
abstract: Preincubating pig erythrocyte membranes with ATP enhances their ability to accumulate Ca(2+) against a concentration gradient. The extent of this increase is dependent on preincubation time over the period 0-60min. As the accessibility of outside membrane markers is decreased by preincubation and as accumulated Ca(2+) is not removed by EGTA [ethanedioxybis(ethylamine)tetra-acetate], it is suggested that ATP causes the formation of sealed inside-out vesicles which can transport Ca(2+) inward. The transport system requires ATP and Mg(2+) and exhibits an apparent dissociation constant for Ca(2+) of approx. 100mum. Since the dissociation constant for Ca(2+)-sensitive ATPase (adenosine triphosphatase) in these preparations is similar, it is concluded that this ATPase is responsible for Ca(2+) transport. Polyphosphoinositide concentrations are also increased during incubation with ATP; however, there is no change in their rate of synthesis or breakdown during Ca(2+) transport.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000097:blood*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D013552:Swine; D013997:Time Factors
chemical_list: D004533:Egtazic Acid; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D008274:Magnesium; D002118:Calcium