Kinetics of (16 123I) Iodohexadecenoic Acid Metabolism in the Rat Myocardium, Influence of Glucose Concentration in the Perfusate and Comparison with (1 14C) Palmitate

External counting, intracellular and subcellular distribution of (16 123I) iodohexadecenoic acid are studied on isolated rat hearts perfused with or without glucose. The presence of an exogenous substrate reduces the fatty acid oxidation and induces an increase of total cardiac and organic fraction activities. In this fraction, activity is very low for free fatty acids, but high for triglycerides and especially for polar lipids. The presence of an exogenous substrate leads to a more active esterification of fatty acids. Coronary effluents analysis shows, in the hydrophilic phase, a lower activity rebound in the presence of glucose. In the mitochondrial fraction, activity is mostly in the organic phase, as polar lipids especially. In the non-mitochondrial fraction, activity is much higher in the aqueous phase. 90 s p.i. of (l 14C) palmitic acid, over 80% of the myocardial activity is found in the hydrophilic fraction, which indicates--as for the iodo fatty acid (IHA)--an immediate and important oxidation, especially without glucose. These data seem to prove that IHA is taken up by the myocardial cells, enters the mitochondria where it is, without an early deiodination, oxidized with iodide release. IHA metabolic changes can be seen on the external detection myocardial activity curve. Omega iodinated fatty acids do not undergo a nonspecific important deiodination and are therefore well adapted to an external study of myocardial metabolism.