Greater than expected alanine aminotransferase activities in plasma and in hearts of patients with acute myocardial infarction.

Early increases in the activity of alanine aminotransferase (ALT, EC 2.6.1.2) in plasma are observed in about 7% of patients with acute myocardial infarction (AMI), of whom about half die. Some type of liver injury, secondary to AMI, could be responsible for this phenomenon. However, quantitative analysis shows that the release of ALT in most of these patients conforms to the myocardial release pattern. Moreover, extra release of hepatic aspartate aminotransferase (EC 2.6.1.1) is not observed. These findings suggest that the heart may occasionally contain a high ALT activity. This hypothesis was verified by determination of enzyme activities in 10 hearts obtained from patients who died after AMI. The mean ALT activity in these hearts, 21 (SD 12) U per gram wet weight, significantly (P less than 0.01) exceeds the value of 7.7 (SD 4.9) U/g found for seven control hearts and may reflect increased amino acid metabolism in the energy-depleted heart muscle, as described earlier for skeletal muscle.