Effect of potassium ion on the response of cobalt chloride to calcium chloride-induced isolated mouse duodenal contraction was observed in calium-free(NK-OC), potassium and calcium-free(OK-OC), and high potassium and calcium-free (HK-OC) Tyrode's
solutions.
Phasic contraction(PC) induced by calcium chloride(CaCl2, 4mM) addition(4mM) was more markedly depressed in potassium-free soultion than in high-potassium soltuion and PC induced by acetylcholine was more markedly depressed in high-potassium
solution
than in potassium free solution. Phasic contraction induced by calcium chloride was more markedly depressed by the of cobalt chloride(CoCl2, 2.6mM) in OK-OC solution than in NK-OC and HK-OC solution, as compared with individual control, Phasic
contraction induced by acetylcholine was not depressed by the presence of CoCl2 in all three kinds of solutions. Ratio of phasic contraction to tonic contraction(P/T) induced by addition of CaCl2 and acetylcholine was little affected by KCl
presence. In
the presence of CoCl2, the ratio induced by CaCl2 was little in KCl-free soultion, but tendency to increase was shown in NK-OC and HK-OC solutions. The ratio induced by acetylcholine was increased by the presence of CoCl2 which was little
effected
by
presence of potassium or not.
These results indicate that potassium ion may affect inhibitory action of cobalt chloride to
calcium chlorideinduced tonic contraction.
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