Time course study of infarct reducing effect of UP. U50,488 H (10 mg kg−1) was given intravenously, and the heart was removed, perfused and subjected to I/R 12, 18, 24, 48 or 72 h later, n=8 in the CON group and n=5–8 in treatment groups. Values are expressed as mean±s.e.m. **P<0.01 vs CON.