['During reperfusion of ischaemic myocardium, Na+/H+ exchange promotes recovery from acidosis resulting in an accumulation of intracellular Na+. This leads to calcium overload via Na+/Ca2+ exchange and might result in cell necrosis contributing to reperfusion injury.', 'We assessed whether HOE 694, a specific inhibitor of Na+/H+ exchange, is able to reduce infarct size in swine myocardium. Experiments were performed in pentobarbitone-anaesthetized, open-chest pigs which were subjected to a 60 min occlusion of the left anterior descending coronary artery (LADCA) followed by 2 h of reperfusion. Three groups of animals were studied. In the pre-reperfusion group (pre-REP, n = 7) HOE 694 infusion (7 mg/kg/15 min) was started at 45 min of occlusion of the LADCA and continued until the end of occlusion, while in pre-occlusion group (pre-TCO, n = 7) HOE 694 infusion was started 15 min before occlusion and stopped at the onset of ischaemia. In the control group (n = 7) animals received vehicle alone. At the end of the protocol, infarct size (as d% of the left ventricular risk region) was determined by the p-nitroblue tetrazolium method. Treatment with HOE 694 prior to the ischaemic insult or upon reperfusion significantly reduced infarct size [4.1%(1.4%), P < 0.01 and 38.2%(5.8%), P < 0.05, respectively], compared with 77.7%(4.0%) in the control group. However, infarct size was significantly more reduced in the pre-TCO group than in the pre-REP group (P < 0.05).'] Does preischaemic as well as postischaemic application of a Na+/H+ exchange inhibitor reduces infarct size in pig?