Abstract
A series of experiments was made to study the chemical changes with reference to lactic acid and glycogen in the myocardium following ligation of the anterior descending branch of the left coronary artery of dogs and to correlate these with the anatomic and electrocardiographic changes observed.
Sixteen dogs were used. Essentially similar operative techniques were employed as in the experiments previously reported. 1 , 2 The tissues for chemical studies were excised from the heart in situ in the living animal under amytal anesthesia and immediately plunged into liquid air. Lactic acid was determined by the method of Friedemann and Graeser 3 and the glycogen by the modified Pflüger procedure as outlined by Yannet and Darrow. 4
In the first group of experiments 10 dogs were used. After ligation of the coronary vessels the animals were sacrificed at intervals varying from 1/2 hour to 24 hours. The lactic acid content of the muscle tissue from the zone supplied by the ligated vessels was increased 100-200% over that of the control zone (right ventricle) while the glycogen content of similar zones was decreased below that of the control zone. These changes were noted in every instance irrespective of the duration of the period of ligation. Control animals subjected to the same operative procedure except that the sutures were passed about the vessels and then removed, showed no significant variation in the content of lactic acid or glycogen from the two sides of the heart.
In the second group of experiments the coronary vessels were ligated for varying periods up to 8 hours. At the end of these intervals the ligatures were removed and the animals were sacrificed 2 hours afterward. Six dogs were used in this series. In all instances the lactic acid content of the heart muscle from the zone supplied by the previously ligated vessels was decreased below that of the muscle from the control zone. The glycogen content of the affected zones, as in the first group, was also decreased below that of the control zone.
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