Effect of glucose on the distribution of iodine-123-IHA-16 between esterification and oxidation in canine myocardium

To evaluate the effect of glucose perfusion on the myocardial metabolism of 123I]-16-iodo-9-hexadecenoic acid (IHA), the latter was injected intravenously into six fasting dogs perfused with a solution lacking glucose (controls) and seven fasting dogs perfused with glucose and insulin. The distribution of myocardial 123I among iodides, free IHA, and esterified IHA was measured in myocardial biopsy specimens. The increase in esterification and decrease in oxidation of IHA due to glucose were quantified using a compartmental mathematical model of myocardial IHA metabolism. Subsequently, in six control and six glucose-perfused dogs, cardiac radioactivity was measured with a scintillation camera for 1 hr following i.v. injection of IHA. Four different methods were used to analyze the myocardial time-activity curves and to calculate the distribution of IHA between oxidation and esterification. Results comparable to those provided by analysis of biopsy specimens can be obtained by considering the curve to be the sum of an exponential and a constant, or by analyzing it with a compartmental mathematical model.