Effect of beta-adrenergic stimulation on free fatty acid content in subepicardial and subendocardial layers of the dog heart in situ. Separation and assay by capillary gas chromatography.

The effects of beta-adrenergic stimulation produced by an infusion of isoproterenol (1 microgram X kg-1 min-1, 30 min) were studied in situ in the anaesthetized dog placed under a total cardiopulmonary bypass. Samples of the subepicardial and the subendocardial layers were homogenized separately prior to the extraction and methylation of free fatty acids (FFA). Gas chromatography on Carbowax 20 M capillary columns was used for the quantitation of myristic (C 14:0), palmitic (C 16:0), palmitoleic (C 16:1), stearic (C 18:0), oleic (C 18:1), linoleic (C 18:2), and arachidonic (C 20:4) acids. Within 5 min, isoproterenol decreased the tissue content of FFA significantly. The decrease was more pronounced in the endocardial layer where the FFA concentration reached its minimum at the 5th or the 15th min. In the epicardial layer, all the FFA reached their minimal concentration at the 30th min of the isoproterenol infusion. In both layers, lactate content remained unchanged at 5 and 15 min and rose at the 30th min only and content in phosphorylated compounds (ATP, creatine-phosphate-CP) did not show any significant variation during the beta-stimulation period. A significant correlation was found between the chronotropic effect of isoproterenol and the reduction of FFA concentration.