[Role of middle-molecule blood peptides in the development of cardiac depression in thermal burns].

Using ultrafiltration and subsequent gel filtration a fraction of middle mass peptides (MMP) possesing cardiodeppressing activity, has been isolated from the blood plasma of dogs exposed to burn injury. In contrast to the corresponding MMP fraction from healthy animal blood, this fraction suppressed contractility of the isolated rat's papillary muscle. Moreover, the active MMP fraction caused an appreciable bradycardia when administered subarachnoidally. The same phenomenon is typical of the corresponding MMP fraction from intact dog's blood, but the rate of bradycardia is significantly lower than that obtained for the fraction from the blood of injured animals. The possibility of local and central-mediated influence of the active fraction on heart functions is discussed. Central-mediated action of the active MMP fraction is confirmed by the ability of other MMP fractions from the blood of injured animals to enhance the blood-brain barrier permeability.