Thermal Injury: Release of an Inhibitor of Adenosine 5′-Triphosphate Induced Muscular Contraction 1

Abstract

Despite increasing recognition of the release of specific toxic substances by thermal injury, relatively little is known about the mechanism by which these substances exert their damaging effects on the host. A toxic glycoprotein prepared from in vitro scalded human skin inhibited the formation of adenosine 5′-triphosphate (ATP)-induced tension by glycerol-extracted muscle fibers (1, 2). The inhibition was independent of calcium or magnesium concentration, but dependent on the glycoprotein concentration (3). Rabbits injected with the toxic glycoprotein developed specific antibodies titers against the glycoprotein. Serum of convalescing burn patients, similar to rabbit antiserum, or its gamma globulin fraction, neutralized the glycoprotein physiological inhibitory activities (4). The sensitivity of the glycerol-extracted muscle fiber to adenosine 5′-triphosphate was inhibited by the “toxic glycoprotein”, but was enhanced by an active protein present in normal human serum (5).

In this investigation, the effects of serum from “acute burn” and “convalescing burn” patients on the development of ATP-induced tension by glycerol-extracted fibers were studied. The inhibitory effect of the acute burn serum was determined at increasing concentrations, and at time intervals during the convalescing period. Neutralization of the inhibitory effect of the acute burn serum by “convalescing burn” serum was determined at intervals of time during the convalescing period. This paper demonstrates the presence of an inhibitor of ATP-induced tension in the serum of acute burn patients. The degree of inhibition was concentration dependent. The acute burn serum inhibitory effect was neutralized by convalescing burn serum.

Methods. Blood samples were obtained from Sumner L. Koch burn ward at Cook County Hospital. The blood was allowed to clot at room temperature, and the serum was separated by centrifugation at 1000g for 10 min. The serum was dialyzed against three 10-fold changes of 62 mM Tris-phosphate buffer, of pH 7.4, containing 2.5 mM MgCl₂, then was frozen at —20° in multiple aliquots for later analysis.