title: Na+-Ca2+ exchange activity in rabbit lymphocyte plasma membranes.
abstract: Plasma membranes of rabbit thymus lymphocytes accumulated Ca2+ when a Na+ gradient (intravesicular greater than extravesicular) was formed across the membranes. Dissipation of the Na+ gradient by the addition of Na+ to the external medium decreased Ca2+ uptake. Ca2+ preloaded into the lymphocytes was extruded when Na+ was added to the external medium. The Ca2+ uptake decreased at acidic pH but increased at alkaline pH (above 8) and the activity was saturable for Ca2+ (apparent Km for Ca2+ was 61 microM and apparent Vmax was 11.5 nmol/mg protein per min). Na+-dependent uptake of Ca2+ was inhibited by tetracaine and verapamil, and partially inhibited by La3+. The uptake was not influenced by orthovanadate.
mesh_terms: D000818:Animals; D002118:Calcium / Q000097:blood*; D002462:Cell Membrane / Q000378:metabolism; D007700:Kinetics; D007811:Lanthanum / Q000494:pharmacology; D008214:Lymphocytes / Q000378:metabolism*; D011817:Rabbits; D012964:Sodium / Q000097:blood*; D013748:Tetracaine / Q000494:pharmacology; D013997:Time Factors; D014700:Verapamil / Q000494:pharmacology
chemical_list: D013748:Tetracaine; D007811:Lanthanum; D012964:Sodium; D014700:Verapamil; D002118:Calcium