A RAPID ISCHEMIA-INDUCED APOPTOSIS IN ISOLATED RAT HEARTS AND ITS ATTENUATION BY THE SODIUM-HYDROGEN EXCHANGE INHIBITOR HOE-642 (CARIPORIDE)

S. CHAKRABARTI, A. N. E. HOQUE AND M. KARMAZYN. A Rapid Ischemia-induc ed Apoptosis in Isolated Rat Hearts and its Attenuation by the Sodium- Hydrogen Exchange Inhibitor HOE 642 (Cariporide). Journal of Molecular and Cellular Cardiology (1997) 29, 3169-3174. Apoptosis is a potentia lly important myocardial response to pathology including ischemia and reperfusion. Na-H exchange (NHE) represents an important mechanism for mediating such injury. The present study was done to determine if NHE inhibition can affect early apoptosis in an acute model of ischemia a nd reperfusion, Isolated rat hearts were subjected to zero-now ischemi a for various durations with or without subsequent 30 min of reperfusi on. Nick-end-labelling of biotin-dUTP (TUNEL staining), as well as DNA extraction followed by agarose gel electrophoresis, were used to semi quantify apoptotic cells and identify DNA laddering, respectively. Apo ptosis first appeared after 10 min of ischemia and reached a maximum l evel after 30 min. The number of apoptotic cells after 30 min of ische mia was 31 +/- 3 per 100 high power microscopic fields, whereas in rep erfused hearts the number of cells was 34 +/- 3, To determine the effe ct of NHE inhibition, hearts were pretreated 15 min prior to ischemia with HOE 642,a potent and specific inhibitor of the isoform (NHE-1) fo und in myocardium. HOE 642 significantly reduced the number of apoptot ic cells in the ischemic and reperfused heart to 2 +/- 1 and 6 +/- 1, respectively (P<0.05 from untreated hearts). DNA laddering was not obs erved with electrophoretic DNA analysis, likely owing to the small num ber of apoptotic cells involved, Hearts recovered nearly 100% of funct ion in both groups, although there was a significantly higher recovery after 1 and 2 min of reperfusion in those hearts treated with HOE 642 , Our study shows that apoptosis, albeit very mild in nature, can be r apidly induced in isolated hearts by a relatively brief period of isch emia without reperfusion, which can be markedly attenuated by the NHE inhibitor HOE 642. The ability of HOE 642 to markedly attenuate apopto sis may be important in terms of understanding the drug's cardioprotec tive properties as well as the overall role of NHE in heart disease. ( C) 1997 Academic Press Limited.