| Abstract: | Experiments on papillary muscles of normal (control) rabbits and of those with the compression syndrome (CS) were made to explore the action of the control and "syndromic" blood plasma on electric and contractile activity of the myocardium. Isometric contractions of myocardial preparations were recorded at varying stimulation frequencies (0.1-2 Hz). Intracellular rest potentials (RP) and action potentials (AP) were led away with the aid of glass microelectrodes filled with 2.5 M KCl. The replacement of Tyrode solution by the control plasma raised the amplitude of papillary muscle contractions, that being greater as regards the muscles from rabbits with the CS. The "syndromic" plasma (diluted by Tyrode solution in a 1:1 ratio) markedly inhibited the amplitude of contractions of papillary muscles from both the control rabbits and animals with the CS. Reduction of the contractions induced by the "syndromic" plasma seen in all the preparations was followed by two patterns of changes in electrical activity of myocardial fibers. In one pattern, the RP, the amplitude and duration of the AP declined. In the other, on the contrary, the changes were reduced to a greater AP duration. The conclusion is made about the absence of a direct relationship between the decrease in myocardial contractility and changes in intracellular potentials induced by the "syndromic" plasma. It is suggested that the "syndromic" plasma deranges the process of stimulation and contraction coupling in heart papillary muscles. |
