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
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.
Subject(s)
Ischemia/metabolism , Myocardium/metabolism , Animals , Cell Hypoxia , Cell Membrane/metabolism , Chlorine/metabolism , Cold Temperature , Electron Probe Microanalysis , Frozen Sections , Glucose/deficiency , In Vitro Techniques , Male , Myocardium/ultrastructure , Papillary Muscles/metabolism , Papillary Muscles/ultrastructure , Potassium/metabolism , Rats , Rats, Wistar , Sodium/metabolismABSTRACT
It has been hypothesized that cardiac ischaemia induces some changes in the cardiac myocyte element. In the present study we analysed whether the imbalance of potassium, sodium and calcium in cardiomyocyte may be coupled with ischaemic conditions, using a perfused heard as a model. Electron Probe Microanalysis (EPMA) of papillary muscle cryosection was employed to examine the intracellular content of elements. Following a 30 min acute ischaemia the intracellular potassium was not changed and sodium was reduced. During a prolonged ischaemia (45 min) [K] loss was shown and [Na] concentration was seen reestablished. These results demonstrate that the active transport of potassium and sodium is possible at the beginning of ischaemia. This suggests that under abaerobic conditions Na-K-ATPase may be functionally coupled with an ATP-sensitive K channel through intracellular messenger, possibly ATP.
