Subject(s)
Hypoxia/metabolism , Muscle Cells/metabolism , Myocardium/metabolism , Potassium/metabolism , Sodium/metabolism , Adenosine Triphosphate/metabolism , Animals , Cell Hypoxia , Cell Membrane/metabolism , Electron Probe Microanalysis , In Vitro Techniques , Ion Transport , Male , Perfusion , Rats , Rats, WistarABSTRACT
Direct effects of cardiotropic preparations on the hearts isolated from Wistar rats were examined. Deenergization of cardiomyocytes was modeled under conditions of hypoxic perfusion. Recovery of cardiac function during reperfusion was assessed by changes in the heart rate and contraction amplitude.
Subject(s)
Heart , Myocardium/metabolism , Animals , Heart/drug effects , Heart/physiology , Heart Rate/physiology , Hypoxia , In Vitro Techniques , Male , Myocardial Contraction/physiology , Rats , Rats, WistarABSTRACT
Electron probe microanalysis was employed to determine the elemental concentration (K,Na,Cl) in a myocyte on cryosections of the papillary muscle of the isolated rat (Wistar) heart. Protocols of global ischemia and ischemic conditions under glucose-free anoxic perfusion were applied. It was shown that global ischemia induces potassium deficiency (94 +/- 2 mM) in the myocyte and an increase in the level of sodium (72 +/- 4 mM) and chlorine (42 +/- 1 mM) in the cytoplasm compared with intact cell (122 +/- 2; 36 +/- 1; 24 +/- 1 mM). Glucose-free anoxic perfusion leads to a smooth fall of potassium concentration in the cell up to 54 +/- 2 mM with the retention of intracellular sodium (40 +/- 1 mM) and chlorine (26 +/- 1 mM) level. The present finding suggest that, in early ischemia, specific membrane mechanisms of ion transport are activated. Among these are KNa channel, Hi(+)-Nao+ exchange, KATP channel, lactate transport from the cell, associated either with potassium efflux to the extracellular space or chlorine influx into the myocyte. It is assumed that Na/K-ATPase is also activated under ischemic conditions.
