The effect of cellular energy reserves and internal calcium ions on the potassium conductance in skeletal muscle of the frog

The Journal of Physiology
R FinkE Wettwer

Abstract

The increase in K+ conductance induced by repetitive stimulation in metabolically poisoned sartorius muscle fibres of the frog was investigated, using a two-micro-electrode voltage-clamp technique. After the inhibition of creatine kinase by 0.4 mM-1-fluoro-2,4-dinitrobenzene (FDNB) and a complete and irreversible exhaustion of contractility, a nearly linear current-voltage relation was measured between -100 and 0 mV. In the presence of CN- (4 mM) an 'intermediate state' could be established by repetitive stimulation towards complete mechanical exhaustion. In this labile state, the high and potential-independent K+ conductance could be induced by repetitive voltage-clamp pulses (100 ms duration) from -85 to 0 mV membrane potential. After the pulses had ceased, fibres regained their original membrane conductance within several minutes. After the electrophoretic injection of the Ca2+-chelating agent H2EGTA2- into fibres in the intermediate state, an increase in membrane conductance by repetitive voltage-clamp pulses could no longer be induced. Fibres in the intermediate state into which H2EGTA2- -buffered Ca2+ (free Ca2+ approximately 10(-5) M) was injected, or to which external caffeine (1.5 mM) was applied, showed a spontaneous ...Continue Reading

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