Decrease in myocardial polyamine concentration in rats with myocardial infarction.

Cardiac polyamines are thought to protect the myocardium against harmful stimuli and to be regulated by sympathetic nerve activation. In the present study, polyamines concentrations in non-infarcted myocardium were investigated. Myocardial polyamines contents decreased significantly in the non-infarcted regions by day 3 in rats with myocardial infarction compared with sham-operated rats and with the untreated control rats. The cardiac catecholamine concentration decreased by day 1 after myocardial infarction. Myocardial ornithine decarboxylase activity also decreased in the non-infarcted regions; suggesting that the decrease in cardiac polyamines contents relate to an insufficiency of the ornithine decarboxylase activity in rats with myocardial infarction. These results suggest that the decrease in polyamines concentrations after myocardial infarction is associated with functional sympathetic nerve denervation and that the vulnerability of the heart after myocardial infarction may be due to a decrease in polyamine concentrations in the non-infarcted region.