Extraction and release of individual free fatty acids by the heart and fat depots.

It has previously been demonstrated (1) that in the postabsorptive state energy production of the heart depends largely on fatty acid metabolism; both esterified and nonesterified or free fatty acids (FFA) are taken up by the heart muscle. Although the general turnover rate of individual FFA has been studied, no investigations have been undertaken to discover their fate in the heart muscle. After administration of C14-labeled palmitic, oleic or linoleic acid which had been bound to albumin in vitro, Fredrickson and Gordon (2) found no difference in fractional turnover rate of these individual FFA in the plasma of the intact subject. General conclusions from these observations are difficult, since Bates and Olson (3) have pointed out that in the animal organism the fate of fatty acids bound to albumin in vitro may be different from that of endogenous FFA. The present study deals with the myocardial extraction of individual FFA. Since, in the course of this investigation, it was found that the rate of myocardial uptake of individual FFA differed, the work was extended to include the release of individual FFA by adipose tissue.