ISSN:
1432-2013
Keywords:
Potassium ions
;
Excitation-contraction coupling
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract 1. Inotropic effects of potassium rich solutions on frog cardiac muscle have been studied both in current clamp and voltage clamp conditions, using a double sucrose gap apparatus. 2. Potassium rich solutions cause either a positive or a negative inotropic effect, together with an increase or a decrease in the duration of the action potential, according to the preparation. 3. The phasic phase of contraction and the slow inward current are decreased in amplitude; the reversal potential of the slow inward current is shifted towards more negative values. 4. The tonic phase of contraction is first decreased, then increased; the effects are correlated with modifications of the background current, initially in the inward, then in an outward direction. 5. The tension level obtained in contracture experiments is increased or decreased, according to the direction of the changes in the background current. 6. The effects of potassium rich solutions are still observed in the presence of ouabain, suggesting that they are independent of any effect on the sodium-potassium pump. 7. The effects of potassium rich solutions are still observed when external sodium is replaced by sucrose; they disappear (except the effect on the background current) when external sodium is replaced by lithium. 8. The results, which indicate that potassium ions play a role in the regulation of the intracellular concentration of calcium ions, are discussed in relation to a possible K/Ca exchange mechanism, to the Na/Ca exchange and to the role of intracellular calcium stores.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00658268
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