MgATP and phosphoinositides activate Na(+)/Ca(2+) exchange in bovine brain vesicles. Comparison with other Na(+)/Ca(2+) exchangers.
We investigated the metabolic modulation of the Na(+)/Ca(2+) exchanger in membrane vesicles obtained from bovine brain. The Na(+)/Ca(2+) exchanger was activated by MgATP with a K(0.5) of 336 micro M. Unlike the squid nerve Na(+)/Ca(2+) exchanger, this effect required no cytosolic component. Also, stimulation is the same in vesicles prepared and/or assayed at the ionic strength found in mammals (160 mM) or marine animals (300 mM). Other differences between squid and bovine nerve are that the bovine brain Na(+)/Ca(2+) exchanger is not stimulated by phosphagens, either phosphoarginine (molluscan source) or phosphocreatine (mammalian source); and that stimulation by MgATP in bovine brain is related to the production of polyphosphatidylinositides. In this regard bovine heart and brain Na(+)/Ca(2+) exchangers behave similarly. These results indicate that the mechanisms of metabolic regulation of the squid and mammalian nerve Na(+)/Ca(2+) exchangers are not alike and represent differences between species. Some differences found between bovine heart and brain exchangers, such as MgATP stimulation even at saturating [Ca(2+)] and the smaller degree of activation by adenosine 5'- O-(3-thiotriphosphate) (ATP-gamma-S) in the brain, may be related to the unequal isoform population in both tissues.
Berberián
Graciela
G
Laboratorio de Biofísica, Instituto de Investigación Médica Mercedes y Martín Ferreyra, Casilla de Correo 389, 5000 Córdoba, Argentina. gelso@immf.uncor.edu
Asteggiano
Carla
C
Pham
Cuong
C
Roberts
Shirley
S
Beaugé
Luis
L
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000493:pharmacokinetics; D002132:Calcium Radioisotopes; D002417:Cattle; D022162:Cytoplasmic Vesicles / Q000378:metabolism; D049832:Decapodiformes; D010455:Peptides / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000494:pharmacology*; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*; D013045:Species Specificity
D002132:Calcium Radioisotopes; D010455:Peptides; D010716:Phosphatidylinositols; D019831:Sodium-Calcium Exchanger; C066745:exchanger inhibitory peptide; C022571:adenosine 5'-O-(3-thiotriphosphate); D000255:Adenosine Triphosphate; D002118:Calcium