Contractility and extractability of heart actomyosin after death.

The contractility and extractability of actomyosin and proteins prepared from dogs' heart immediately , and one hour after death were compared. The yield of total and soluble proteins and of actomyosin was found to be identical. In addition, there was no difference between the after-loaded contractions of actomyosin bands of fresh preparation and those obtained one hour after death. S TUDIES on patients suffering from con-gestive failure have shown no abnormality in the extraction and utilization of glucose, pyruvate, lactate, fatty acids, amino acids and ketone bodies by the human heart. This finding has suggested that the basic defect in the heart muscle in myocardial failure is primarily in mechanisms concerned with energy utilization. 1 Similar conclusions were reached by Benson 2 who, by producing experimental chronic failure in dogs, was able to show that actomyosin from failing hearts differed from that of normal hearts. To the present, no experiments have been published which deal with changes of actomyosin of failing human heart muscle. Such investigations could be carried out by comparing actomyosin obtained from heart muscle of patients who died of con-gestive failure with actomyosin obtained from normal hearts. Since these studies are based on the premise that characteristic properties of actomyosin do not change for a brief period after death, an investigation was begun which deals with a comparison of properties of acto-myosin prepared from dogs' hearts immediately after death and one hour later. METHODS Eleven adult dogs were anesthetized by the intravenous injection of sodium pentobarbital (30 mg./Kg. weight). The chest was then entered and approximately 15 Gm. of left ventricular muscle were excised. The dead animal was then left on the table at room temperature. One hour later another portion of left ventricular muscle was excised. In both instances actomyosin (myosin-B) was extracted from the specimen, using a modification of the method reported by Benson, Holloway and Freier. 3-* All procedures were carried out in the cold room at a temperature of 1C. The muscle was minced with iris scissors and 10 Gm. were homoge-nized ina Waring blender for 3 min., with a fourteen-fold volume of Weber-Edsall solution. The muscle was then extracted for 24 hours at 6C. in a twenty-fold volume of Weber-Edsall solution to which the disodium salt of ATP was added to make a total concentration of .015 per cent ATP. After extraction, the homogenate was mixed gently by shaking it and a …