MATERIALS AND METHODS

Most of the methods used in this investigation have been described in detail in previous studies from this laboratory. Coronary sinus blood was obtained from a catheter placed in the coronary sinus, and blood sam-ples from metabolic studies were simultaneously obtained from arterial and coronary sinus blood (1). The coro-nary blood flow was determined with the nitrous oxide desaturation method (4). Blood glucose was determined by the method of Hagedorn and Jensen (5) using Somogyi's method to prepare the blood filtrate (6). The manometric method of Van Slyke and Neill was used for blood oxygen analyses (7). Total fatty acids (TFA) were determined according to the method of Man and Gildea (8) based on the Stoddard and Drury method (9). According to these investigators, the error of this method is±5 per cent. However, modification of their original procedure developed by Siegel (10) resulted in the variance of the difference between two observations of only 0.000232 and a standard error of the difference of 0.015 (Table I). In the procedure employed in this