Basic nuclear proteins (histones) alter actomyosin ATPase activity in vitro and depress cardiac contractile force in vivo, suggesting a potential role in modulating cardiac function.
Histone effects on contractility remain hypothesis-generating in animals; leaves open any role in human cardiac disease.
A method for the preparation of semipurified basic proteins from cardiac muscle was presented. At low ionic strengths (below 0.05) and in the presence of Mg ++ , these compounds, as well as purified histones from a variety of tissues, inhibited the Mg ++ - ATP ase activity of cardiac and skeletal muscle actomyosin or myofibrillar suspensions. Under similar conditions, a retardation of superprecipitation occurred. At high ionic strengths (above 0.06) the histones stimulated the Mg ++ - ATP ase. In the presence of Ca ++ , and at all ionic strengths studied, the histones elicited a marked stimulation of actomyosin ATP ase. Administration of histones to anesthetized, open-chest guinea pigs, caused a significant depression of the force of contraction of the hearts. These data suggest a possible involvement of basic nuclear proteins in cardiac activity.
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Schwartz et al. (1965) studied this question.
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