Effects of "acute burn serum inhibitor" and "relaxing factors" on papillary muscles contractility.

Abstract

The main findings described in the present studies are: a) Depression of developed tension in papillary muscles from human and dog quiescent hearts, and rabbit, guinea pig and rat hearts with an “acute burn serum inhibitor—ABSI”. The papillary muscles from human or dog quiescent hearts were restored to responsiveness to electrical stimulation with “ultrasonication modified epinephrine”. b) Inhibition of Ca+2 uptake by the microsomal fractions of the cardiac muscles, and adenosine triphosphatase activity with the “acute burn serum inhibitor”. c) The depressing and inhibitory effects of“ABSI” are reversed with “ultrasonication modified digitoxin”. d) Depression of developed tension in papillary muscles and inhibition of Ca+2 uptake by the microsomal fractions, and adenosine triphosphatase activity of the cardiac muscle with the “relaxing factor” of the sarcoplasmic reticulum fragments: The magnitude of the inhibition varied from one relaxing factor to another, and depended on the actomyosin preparation. Since the same isolation procedure was employed in preparing the “Relaxing Factor” from various species, the differences presented suggest differences in the structural constitution of the relaxing factor which are species dependent.