Blockade by zinc ions of K(+)-induced contraction and calcium in guinea pig Taenia coli.
Preincubation with 0.3 mM Zn2+ markedly inhibited both the tonic response and Ca2+ binding at low affinity sites induced by K+ (60 mM), with smaller effects on the phasic response and the high affinity Ca2+ sites, in Taenia coli. However, when the muscle was kept in Zn(2+)-containing medium following the first stimulation with the K+, the phasic response and the high affinity Ca2+ sites were more severely inhibited during the second stimulation with K+. This probably indicates that Zn2+ reduced the tonic tension response to K+ mainly by inhibiting Ca2+ influx at the cell membranes of Taenia coli. However, when Zn2+ is continuously present, Ca2+ is not supplied at the storage sites and is not available for the phasic response to a second stimulation with K+.
Nasu
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Department of Veterinary Pharmacology, Faculty of Agriculture, Yamaguchi University, Japan.
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D003106:Colon / Q000187:drug effects / Q000502:physiology*; D006168:Guinea Pigs; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology*; D015032:Zinc / Q000378:metabolism / Q000494:pharmacology*
D015032:Zinc; D011188:Potassium; D002118:Calcium