Effect of isoproterenol on the metabolism of myocardial fatty acids.

The effect of beta-adrenergic stimulation on myocardial fatty acid metabolism was studied in the anesthetized open-chest dog. Isoproterenol (1 microgram/kg/min) was infused; and samples of arterial blood and of left ventricular wall were taken at the 5th min for the determination of the following variables: in arterial blood: lactate and serial free fatty acids (FFA); in myocardial tissue: creatine phosphate (CP), ATP, lactate, carnitine, acylcarnitine, glycerol, and the fatty acid content of each of phospholipids (PL), cholesterol esters (CE), triglycerides (TG), diglycerides (DG), monoglycerides (MG), and FFA. A capillary gas chromatography was used for fatty acid assay. Isoproterenol decreased the content of creatine phosphate but not of ATP. Lactate increased in both arterial blood and myocardial tissue. The five-fold increase in arterial FFA (P less than 0.001) was accompanied with a significant increase in FFA serum/tissue ratio. Free carnitine decreased and acylcarnitine increased. Triglycerides content (which is expressed in terms of its total fatty acid content) was considerably reduced by beta-stimulation in comparison with control group (2694 +/- 689 vs. 7518 +/- 833 nmol/g wet wt, P less than 0.001), and tissue glycerol increased (P less than 0.01). The decrease in total MG content was significant, but not that of DG, nor that of CE. Total PL content did not change. The most marked individual changes (except in PL) were observed on monounsaturated fatty acids, 18: 1 omega 9, 18: 1 omega 7, and 16: 1 cis. The significant changes of monounsaturated/saturated and of 16:1 cis/16:1 trans ratios, in arterial FFA and tissue TG, suggested modifications in the distribution of fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)