This study was designed to investigate the cardioprotective effect of pretreatment with -glucan, the glucose polymer derived from the yeast Saccharomyces cerevisiae, against isoprenaline (ISO)-induced myocardial injury in rats by studying biochemical cardiac markers, antioxidant parameters, apoptosis, ECG and histopathological changes. Male Sprague-Dawley rats were randomly divided into four treatment groups, namely control, -glucan, isoprenaline and -glucan+isoprenaline. The -glucan treatment group received -glucan (50mgkg(-1)day(-1), p.o.) for 10 days. Myocardial injury was induced by ISO administration (100mgkg(-1), s.c.) twice, at an interval of 24h, on the 9th and 10th days. Isoprenaline administration resulted in a marked increase in heart rate, ST segment elevation, myocardial malondialdehyde content, cardiac marker levels (lactate dehydrogenase, creatine kinase-MB and high-sensitivity cardiac troponinT) and apoptotic index, and a significant decrease in R-wave amplitude and myocardial superoxide dismutase, catalase and glutathione peroxidase activities. In addition, apoptosis, congestion, necrosis, inflammatory cell infiltration and myofibrillar disorganization were observed histologically in myocardial tissue sections. The oral pretreatment with -glucan prevented almost all the parameters of isoprenaline-induced myocardial injury in rats, and these findings were confirmed by the histopathological analysis. These findings provide evidence that -glucan could protect rat myocardium against ISO-induced myocardial injury, and this was attributed to its antioxidant and anti-apoptotic properties.