EXPRESSION OF THE Na+/H+ EXCHANGER 1 (NHE1) IN RAT HEART MITOCHONDRIA.

VILLA-ABRILLE, MC; CINGOLANI, HE; ALVAREZ, BV

Buenos Aires, Argentina

Congreso; XVII Meeting ISHR Latin American Section- XXVII National Congress of Cardiology (FAC); 2009

International Society for Heart Research (Latin Section) - Federación Argentina de Cardiología

Electroneutral Na+/H+ exchange activity by NHE is a key component of mitochondrial volume and Ca2+ homeostasis. The molecular identity of the NHE expressed at the inner membrane of the mitochondrion is still controversial. To date, ten mammalian NHE isoforms (NHE1 to NHE10) have been identified, displaying considerable differences in their primary structures, tissue distribution, membrane localization, biochemical and pharmacological properties, and responsiveness to different stimuli. We characterized the expression of the sarcolemmal NHE1 in mitochondria isolated from adult rat hearts, by immunoblot. A ~88 kDa band, corresponding to fully-glycosylated NHE1 protein was detected by a goat polyclonal antibody in mitochondrial lysates obtained from adult rat left ventricles. NHE1 was also identified, and immunoprecipitated, with a rabbit polyclonal antibody, using rat heart mitochondrial lysates. Confocal microscopy studies conducted in freshly isolated rat heart cardiomyocytes, showed localization of NHE1 in the intercalated disc regions, with additional staining of the nuclei and cell periphery. Interestingly, NHE1 co-localized with citochrome C oxidase Complex 1 protein, a marker of mitochondrial inner membrane, suggesting localization of NHE1 in the mitochondria. We proposed that NHE1 may be the Na+/H+ exchanger involved in the regulation of intramitochondrial Na+ and H+ levels.