Adenosine diphosphate effect on contractility of human muscle actomyosin: inhibition by ethanol and acetaldehyde.

Magnesium adenosine triphosphate (Mg-2+-ATP) is known to produce dissociation of muscle actin and myosin in vitro, while its hydrolysis leads to reassociation. The interaction of purified actin and myosin from human muscle, in the presence of Mg-2+-ATP, was stimulated by minute amounts of adenosine diphosphate (ADP), a product of ATP hydrolysis. By contrast, the dissociation of the actomyosin complex was inhibited by ADP. These data suggest that ADP serves to modulate muscle contraction. Ethanol and its primary metabolite, acetaldehyde, inhibited these effects of ADP. The inhibition was reversible when the preparations were freed of these compounds. The effects of ethanol and acetaldehyde on the response of actomyosin to ADP may play a role in the pathogenesis of alcoholic myopathy and cardiomyopathy.