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SOURCES OF CALCIUM FOR CONTRACTION OF GUINEA‐PIG ISOLATED TRACHEAL SMOOTH MUSCLE
Author(s) -
Creese B. R.,
Denborough M. A.
Publication year - 1981
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1981.tb00149.x
Subject(s) - contraction (grammar) , guinea pig , calcium , muscle contraction , chemistry , anatomy , endocrinology , medicine , biology
SUMMARY 1. Contractile responses of guinea‐pig tracheal smooth muscle to KC1, histamine, acetylcholine and prostaglandins were reduced after the removal of extracellular Ca 2+ from the bathing medium. 2. KCl‐induced contractures were more dependent on extracellular Ca 2+ than acetylcholine‐induced responses, but less so than histamine‐induced contractures. 3. Responses to high concentrations of contractile agents were less dependent on extracellular Ca 2+ than those to low concentrations. 4. Repeated additions of histamine or acetylcholine in the absence of extracellular Ca 2+ resulted in progressively smaller contractile responses. 5. Treatment of tracheal muscle with EGTA considerably inhibited drug‐induced contractures and abolished the response to KCl. 6. It is concluded that contractile responses of guinea‐pig tracheal smooth muscle involve both the influx of Ca 2+ from the extracellular space and release of Ca 2+ from intracellular sites. The relative contributions of these two Ca 2+ sources depend on both the contractile agent and its concentration. Intracellular Ca 2+ stores may be depleted by treatment with EGTA, or by repeated drug additions in the absence of extracellular calcium.