[Change in the contractile activity of the rabbit myocardium as a result of burn shock of different duration].

Experiments were carried out on the papillary muscles prepared from the rabbit heart 10, 60 or 180 minutes after exposure of the animals to thermal burn. Isometric tension in the changing stimulation frequency of the preparation (the range being 0.1-2.0 Hz) and in post-stimulating potentiation was recorded. It was shown that the disturbance degree of the myocardial contractile activity caused by the burn rose depending on increased shock duration. It was evidenced by the following findings: in all the papillary muscles prepared 3 hours after burn and in 50% of the preparations taken one hour after the injury the "biphasic" dependence frequency power (F-P) peculiar to healthy myocardium changed to "monophasic" one (contraction amplitude progressively decreased on the frequency growing), and poststimulating potentiation, absent in the normal myocardium state, appeared. Within 10-minute shock duration only several preparations revealed poststimulating potentiation, F-P changes being absent. Normal rhythmoinotropic relationships in the myocardium restored under the influence of two-fol increase of (Ca2+)o or under prolonged (3-4 hours) perfusion of the preparation with normal Tyrode's solution. The changes observed in the myocardium rhythmoinotropic relationships produced by the burn shock were similar to those occurred as a result of the calcium canals block by the compound D-600.