Superprecipitation of hybrid actomyosin containing pathologic actin from failing hearts of adults and infants.

Superprecipitation (SP) of artificial actomyosin, obtained by hybridization of Straub actin from the human myocardium with myosin of normal animal hearts was studied. Actin was prepared from the myocardium of persons who died of congestive heart failure and various non-cardiac diseases, as well as of infants whose death resulted from toxic pneumonia complicated or not with heart failure. It was shown that, in the control hybrid actomyosin, the substitution of normal Straub actin by that from the failing heart resulted in decrease of both the rate and extent of SP. The conclusion was made that both changes in myosin properties and Straub actin underlie the reduced contractility of the myofibrillar protein system in acute and congestive heart failure.