title: ATP-driven Ca2+ pump in the basolateral membrane of rat kidney cortex catalyzes an electroneutral Ca2+/H+ antiport.
abstract: An ATP-driven Ca2+ pump in the basolateral membrane of rat kidney cortex pumps Ca2+ out of the cell at the expense of MgATP (Km = 0.191 mM). This pump has a high affinity for free Ca2+ (26 nM). Vanadate, lanthanum, N-ethylmaleimide and calmodulin inhibitor R24571 inhibited this pump activity. Dimethyl[2-14C]oxazolidine-2,4-dione [( 14C]DMO) was entrapped in the vesicles in association with the ATP-driven Ca2+ influx. The ATP-driven Ca2+ influx was stimulated by the intravesicular acid pH and an upper convex Lineweaver-Burk reciprocal plot suggested two possible kinetics; one is that this Ca2+ pump is an allosteric enzyme with more than 1.72 H+ binding sites and another is the presence of two Ca2+ pumps with different affinities for H+. Valinomycin study indicated that the ATP-dependent Ca2+ transport by the BLMV was electroneutral and voltage independent. These results strongly suggest that the ATP-driven Ca2+ pump in the renal basolateral membrane catalyzes an electroneutral Ca2+/H+ antiport.
authors.affiliation: Department of Medicine, Kitasato University School of Medicine, Kanagawa, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Tsukamoto
authors.forename: T
authors.initials: T
authors.lastname: Tamura
authors.forename: F
authors.initials: F
authors.lastname: Marumo
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000201:enzymology*; D008564:Membrane Potentials; D051381:Rats; D011919:Rats, Inbred Strains; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D014634:Valinomycin; D000001:Calcimycin; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium