Expression of cardiac sarcolemmal Na+-Ca2+ exchange activity in Xenopus laevis oocytes.
Injection of Xenopus laevis oocytes with rabbit heart poly(A)+RNA results in expression of Na+ inside (Nai+)-dependent Ca2+ uptake activity. The activity was measured by first loading the oocytes with Na+ using nystatin and then incubating the oocytes in K+ or Na+ medium containing 45Ca. The expressed Na+ gradient-dependent Ca2+ uptake was five to eight times that observed with water-injected oocytes or with poly(A)+RNA-injected oocytes for which the Na+ load step had been omitted. Induced activity was related to the amount of RNA injected and was insensitive to nifedipine. Fractionation of the poly(A)+RNA on a sucrose gradient determined that the active message had a size range between 3 and 5 kb. The properties of the Na+ gradient-dependent Ca2+ uptake indicated that Na+-Ca2+ exchange activity had been expressed in X. laevis oocytes. The result may be useful for cloning and identifying the molecular component responsible for Na+-Ca2+ exchange.
Longoni
S
S
Department of Medicine, University of California, Los Angeles School of Medicine 90024-1760.
Coady
M J
MJ
Ikeda
T
T
Philipson
K D
KD
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism*; D011061:Poly A / Q000235:genetics / Q000302:isolation & purification; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics; D011817:Rabbits; D012508:Sarcolemma / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger; D014982:Xenopus laevis
D002352:Carrier Proteins; D012333:RNA, Messenger; D019831:Sodium-Calcium Exchanger; D011061:Poly A; D012313:RNA; D002118:Calcium