Studies of actomyosin from cardiac muscle of dogs with experimental congestive heart failure.

Comparative studies wore made on cardiac actomyosin from normal dog's and .from dogs with experimental heart failure. Actomyosin was characterized by ultracentrifugal sedimentation velocity, viscosity and ATP-ase measurements. The data on actomyosin from normal cardiac muscle showed a striking' similarity to the findings reported by others for skeletal muscle actomyosin. The only difference found between cardiac actomyosin from the normal and experimental material was an abnormal component (SJOW = 5.0-6.7) iu the sedimentation pattern for actomyosin from 4 of 11 dog's with cardiac failure. It seems likely that the changes in actomyosin which resulted in the abnormal sedimentation pattern were produced duringextraction or preparation of the actomyosin and that they do not reflect an altered state of actomyosin in the functioning heart. The explanation for the occurrence of this slow sedimentation component solely in the experimental material is not clear.