title: The Na+-Ca2+ exchange system in vascular smooth muscle cell membrane vesicles isolated from cultured cells and from tissue is similar.
abstract: The existence of a Na+-Ca2+ exchange system was investigated in sarcolemmal vesicles isolated from cultured cells of dog mesenteric artery. When Na+-loaded membrane vesicles were suspended in a Na+-free KCl medium to create an outwardly directed Na+ concentration gradient across the membrane, a time-dependent uptake of Ca2+ was observed. This uptake of Ca2+ was drastically reduced when the vesicles were suspended in NaCl medium to eliminate the Na+ concentration gradient across the membrane. Monensin also decreased Ca2+ uptake in Na+-loaded vesicles. The apparent Km for Ca2+ was 2.97 microM and the apparent maximum velocity was 4.27 nmol/min per mg protein. The data indicate that a Na+-Ca2+ exchange system exists in sarcolemmal membranes isolated from cultured cells and that it is similar to the system in membranes isolated from the tissue.
authors.affiliation: Department of Pharmacology and Cell biophysics, University of Cincinnati College of Medicine, OH 45267-0575.
authors.forename: M A
authors.initials: MA
authors.lastname: Matlib
authors.forename: M
authors.initials: M
authors.lastname: Kihara
authors.forename: C
authors.initials: C
authors.lastname: Farrell
authors.forename: R C
authors.initials: RC
authors.lastname: Dage
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000302:isolation & purification* / Q000378:metabolism; D002478:Cells, Cultured; D004285:Dogs; D008297:Male; D008565:Membrane Proteins / Q000302:isolation & purification* / Q000378:metabolism; D008638:Mesenteric Arteries / Q000032:analysis; D009131:Muscle, Smooth, Vascular / Q000032:analysis*; D011188:Potassium / Q000378:metabolism*; D012508:Sarcolemma / Q000032:analysis; D019831:Sodium-Calcium Exchanger
chemical_list: D002352:Carrier Proteins; D008565:Membrane Proteins; D019831:Sodium-Calcium Exchanger; D011188:Potassium; D002118:Calcium