Physiologic modelling of MM creatine kinase isoforms

We assessed the kinetics in vivo of isoforms of the MM isoenzyme of creatine kinase. A linear model accounting for plasma conversion of tissue isoform to two other isoforms and disappearance of each from the circulation was tested by non-linear least squares approximations to time-activity profiles of isoforms injected intravenously in dogs. The model was validated by analysis of disappearance rate constants after injections of isoforms with plasma conversion inhibited. The data show that disappearance is the primary route of egress of isoform activity from the circulation and the tissue isoform has the fastest disappearance rate.