Inside-out Vesicles of Membrane Red Cells as a Tool to Validate the competence Among Calcium and Divalent Cations on Plasma Membrane Calcium ATPase.

MARTIARENA JORGE; ROSSI, J.P.F.C.

San Salvador de Bahía, Brasil

Congreso; World Congress of Pharmacy and Pharmaceutical Sciences 2006,; 2006

PHARMACEUTICAL SOCIETIES

DEVELOPMENT OF A METHODOLOGY TO MEASURE THE EFFECT OF DIVALENT CATIONS ON THE TRANSPORT OF CALCIUM BY THE PLASMA MEMBRANE CALCIUM PUMPJ. L. Martiarena and J.P.F.C. Rossi. Departamento de Química Biológica (IQUIFIB) Fac. de Farmacia y Bioquímica, Junín 956, Buenos Aires, Argentina The plasma membrane calcium pump (PMCA) is a fundamental mechanism to remove Ca2+ from the cytoplasm of all eukaryotic cells. PMCAs, like all members of the superfamily of P-type ATPases catalyze the hydrolysis of ATP. There are four genes encoding mammalian PMCAs. The diversity of PMCAs is further increased by alternative RNA splicing that generates more than 20 different variants. At the protein and tissue level, the expression of many of these PMCA isoforms has been confirmed by detection with specific antibodies. The main cation transported by PMCA is Ca2+, although other divalent cations (C2+) also seem to be transported. However reports about C2+ transport are rather controversial. We reported here a method to measure the active transport of C2+ in inside-out vesicles prepared from human red cell membranes. Volume changes were followed recording the intensity of light scattered by a suspension of these vesicles which express mostly PMCA 4b. Results obtained by this methodology showed that (a) it is possible to quantify the transport of Ca2+ measuring the slope of light intensity as a function of time; (b) the influence of drugs that could be inhibitors and activators of PMCA; (c) the transport of divalent cations like Zn2+, Ni2+,Ba2+, Sr2+, Pb2+ and (d) the competence among C2+ and Ca2+.These results show that the method is useful to assay the effect of C2+ different from calcium and drugs present in pharmaceutical preparations that are hazardous for human health. With grants of ANPCYT, UBACYT and CONICET.