Yonsei Med J.  1995 Apr;36(2):146-152. 10.3349/ymj.1995.36.2.146.

Intracellular acidosis decreases the outward Na(+)-Ca2+ exchange current in guinea pig ventricular myocytes

• Lee EH
• Park SR
• Paik KS
• Suh CK

• KMID: 699820
• DOI: http://doi.org/10.3349/ymj.1995.36.2.146

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.

Keyword

Na+-Ca2+ exchange; intracellular pH; cardioplegia; ischemia; acidosis

MeSH Terms

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