Plasma enzymes in myocardial infarction Application of a two-compartment model in assessing myocardial release of enzyme

Abstract

The time dependent appearance (appearance function) of creatine kinase, aspartate aminotransferase and lactate dehydrogenase into plasma of 29 patients suffering from myocardial infarction has been calculated.

The model for calculating the appearance function was based on the assumption of distribution of enzymes into two compartments, plasma and extra-vascular.

The values of exchange rate constants for enzymes between the compartments were chosen on the basis of rate constants for proteins with molecular weights similar to the three enzymes.

The order of magnitude of enzyme catabolism in each of the compartments was unknown. Assumptions of different ratios between catabolism in the two compartments led to highly significant changes in the appearance functions for the enzymes.

Appearance functions for each patient of creatine kinase and aspartate aminotransferase showed almost identical patterns provided adequate catabolic constants were used, whereas the appearance function of lactate dehydrogenase differed from those of the two other enzymes.

Key Words:

• appearance function
• aspartate aminotransferase
• catabolic constants
• creatine kinase
• enzyme turnover
• lactate dehydrogenase