Physiological and molecular characterization of the Na+/Ca2+ exchanger in human platelets.
In this report, we have demonstrated that Na+/Ca2+ exchanger activity in a human megakaryocytic cell line (CHRF-288 cells) is K+ dependent, similar to the properties previously described for Na+/Ca2+ exchange activity in human platelets. With the use of RT-PCR techniques and mRNA, the exchanger expressed in CHRF-288 cells was found to be identical to that expressed in human retinal rods. Northern blot analysis of the mRNA for the human retinal rod exchanger in CHRF-288 cells revealed a major transcript at 5.8 kb with two minor bands at 4.9 and 6.8 kb. mRNA for the retinal rod exchanger was also identified in human platelets. Using Ba2+ influx as a measure of Na+/Ca2+ exchange activity in human platelets, we have demonstrated that exchange activity is driven by the transmembrane gradient for K+ as well as that for Na+. We propose that the K+ dependence of the platelet Na+/Ca2+ exchanger could make platelets especially sensitive to daily fluctuations in salt intake.
Kimura
M
M
Hypertension Research Center, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, New Jersey 07103, USA. kimurama@umdnj.edu
Jeanclos
E M
EM
Donnelly
R J
RJ
Lytton
J
J
Reeves
J P
JP
Aviv
A
A
D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D006801:Humans; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000235:genetics / Q000378:metabolism*
D012333:RNA, Messenger; D019831:Sodium-Calcium Exchanger; D002118:Calcium