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Effects of zinc ions on Ca 2+ uptake during histamine‐induced contraction in guinea‐pig taenia coli
Author(s) -
Nasu Tetsuyuki
Publication year - 2000
Publication title -
fundamental and clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.655
H-Index - 73
eISSN - 1472-8206
pISSN - 0767-3981
DOI - 10.1111/j.1472-8206.2000.tb00442.x
Subject(s) - histamine , taenia coli , stimulation , chemistry , contraction (grammar) , zinc , biophysics , intracellular , calcium , receptor , endocrinology , medicine , biochemistry , biology , organic chemistry
— The present study was undertaken to clarify the effects of zinc ions (Zn 2+ ) on Ca 2+ uptake during histamine‐induced contraction in guinea‐pig taenia coli. Zn 2+ (0.3 mM) had smaller effect on the initial phasic response to 10 −5 M histamine accompanied with decreased Ca uptake at the high affinity sites, while it inhibited the tonic response by inhibiting Ca 2+ uptake at the low affinity sites. After the first stimulation with histamine in the presence of Zn 2+ , the Ca 2+ binding at high affinity sites was not significantly recovered in the presence of Zn 2+ . A second stimulation with histamine in the presence of Zn 2+ did not elicit any phasic response. Furthermore, after β‐escin treatment of the fibres, which leaves receptor‐coupled signal transduction including the Ca 2+ storage sites intact, the contraction due to 10 −5 M histamine was not so affected by 0.3 mM Zn 2+ , but, after resuspension in a solution of pCa 5, 10 −5 M histamine of second application did not elicit the contraction in the presence of Zn 2+ . These results suggested that Zn 2+ does not affect the histamine‐induced Ca 2+ release from the intracellular storage sites in taenia coli. However, when Zn 2+ is present, Ca 2+ is not supplied to the storage sites for the phasic response due to second stimulation with histamine. In addition, Zn 2+ reduced the tonic response to histamine mainly by inhibiting Ca 2+ influx through receptor‐operated and/or voltage‐dependent Ca 2+ channels.