Intracellular acidosis decreases the outward Na(+)-Ca2+ exchange current in guinea pig ventricular myocytes.
10.3349/ymj.1995.36.2.146
- Author:
Ek Ho LEE
1
;
So Ra PARK
;
Kwang Se PAIK
;
Chang Kook SUH
Author Information
1. Department of Physiology, Inha University College of Medicine, Inchon, Korea.
- Publication Type:Original Article ; Research Support, Non-U.S. Gov't
- Keywords:
Na+-Ca2+ exchange;
intracellular pH;
cardioplegia;
ischemia;
acidosis
- MeSH:
Acidosis/*metabolism;
Animal;
Calcium/*metabolism;
Electric Conductivity;
Guinea Pigs;
Heart Ventricle/metabolism;
Hydrogen-Ion Concentration;
Ion Transport;
Myocardium/*metabolism;
Sodium/*metabolism;
Sodium-Hydrogen Antiporter/physiology;
Support, Non-U.S. Gov't
- From:Yonsei Medical Journal
1995;36(2):146-152
- CountryRepublic of Korea
- Language:English
-
Abstract:
The Na(+)-Ca2+ exchange transport operating in outward mode has been suggested to cause Ca2+ entry during reperfusion or reoxygenation, exchanging extracellular Ca2+ for intracellular Na+ that has accumulated during ischemia or cardioplegia. During cardioplegia, however, an increase in Ca2+ entry via this mechanism can be decreased due to increased intracellular H+ activity and a decrease in cellular ATP content. In this study giant excised cardiac sarcolemmal membrane patch clamp technique was employed to investigate the effect of cytosolic pH change on the Na(+)-Ca2+ exchanger, excluding the effect of ATP, in guinea pig cardiac myocytes. The outward Na(+)-dependent current, which has a characteristics of Hill equation, was decreased as pH was decreased in the range of 7.5-6.5. The current density generated by the Na(+)-Ca2+ exchange transport was 56.6 +/- 4.4 pA/pF (Mean +/- S.E.M.) at pH 7.2 and decreased to 42.9 +/- 3.0 pA/pF at pH 6.9. These results imply that Na(+)-Ca2+ exchange transport, operating in a reverse mode during cardioplegia, decreases due to increased intracellular H+, and further suggest that consequent intracellular Na+ accumulation is one of aggravating factors for Ca2+ influx during reoxygenation or reperfusion.
