A new method for studying the incorporation of nonesterified fatty acids into cardiac lipids by using deuterium-labelled palmitate.

A new method for measuring the incorporation of exogenous fatty acids into myocardial lipids of working rat hearts using deuterium-labelled palmitate has been developed. After perfusing isolated hearts, the fatty acid composition of triglycerides, diglycerides, monoglycerides, cholesterol esters, and nonesterified fatty acids (NEFA) was measured by a mass fragmentographic method. Hearts perfused only with 5 mM glucose and 1 mM lactate perfusion as basic substrates showed a significant decrease of triglyceride content, while the other lipids were not found to be significantly reduced. The fatty acid composition of all lipids were not affected. An addition of D31-palmitate complexed to albumin at a molar ratio of 5:1, caused a dose-dependent incorporation into triglycerides and diglycerides which suggested saturation kinetics. The tissue content of nonesterified D31-palmitate was found to be linearly related to its concentration in the perfusate. It may be of note that the concentration of the other NEFA was significantly affected neither by a fatty-acid-free perfusion nor by a perfusion with D31-palmitate. A significant incorporation of the supplied fatty acid into cholesterol esters and monoglycerides could not be detected.