The stoichiometry of Na-Ca+K exchange in rod outer segments isolated from bovine retinas.
Ca2+ extrusion in the outer segments of retinal rods (ROS) is mediated by a protein that couples both the inward Na+ gradient and the outward K+ gradient to Ca2+ extrusion. Na(+)-stimulated Ca2+ release from ROS requires internal K+ and is accompanied by release of internal K+, whereas a slow component of Na(+)-stimulated Ca2+ release does not require K+. In this paper we discuss our observations on the K+ transport via Na-Ca+ K exchange in bovine ROS, on the electrogenicity and stoichiometry of the ROS Na-Ca+ K exchanger, and on the mechanism on coupling Ca2+ to K+ via this protein. Finally, we discuss briefly the physiological implications of Na-Ca+ K exchange.
Schnetkamp
P P
PP
Department of Medical Biochemistry, University of Calgary, Alberta, Canada.
Basu
D K
DK
Szerencsei
R T
RT
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D004563:Electrochemistry; D007474:Ion Exchange; D007700:Kinetics; D011188:Potassium / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000737:chemistry / Q000378:metabolism*; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*
D012964:Sodium; D012413:Rubidium; D011188:Potassium; D002118:Calcium