Expression of the sodium-hydrogen exchanger (NHE-1) in infarcted rat myocardium measured by competitive RT-PCR

The sodium-hydrogen exchanger (NHE) functions as one of the major intracellular pH regulatory mechanisms by extruding one H+ in exchange for one Na+. NHE-1 is the main isoform found in mammalian myocardium. It is activated in response to ischemia and reperfusion and contributes to tissue injury. The aim of this study was to examine the regulation of myocardial NHE-1 in heart after myocardial infarction. Heart tissue was sampled from left ventricle of surgically induced small and large myocardial infarctions (subdivided into infarction area, border zone and remote area) and from sham operated rat hearts, one and six weeks after operation. mRNA was isolated with Dynabeads Oligo (dT)25 and competitive RT-PCR was performed using rTth DNA polymerase. The target mRNA concentration was estimated from a standard curve consisting of different amounts of standard and a constant amount of competitor. Samples and standard curve were amplified by specific 17/18-mer NHE-1 primers in the same RT-PCR assay and run on the same agarose gel to minimize differences due to interassay variation. NHE-1 mRNA expression in remote area of small infarctions was about three times higher than in remote area of large infarctions and sham operated hearts at one and six weeks.