Age-related changes in gallbladder contractility and cytoplasmic Ca2+ concentration in the guinea pig

J. Ishizuka, M. Murakami, G. A. Nichols, C. W. Cooper, G. H. Greeley, J. C. Thompson

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    Abstract

    Gallbladder (GB) motility diminishes with aging. This study was performed to characterize mechanisms that are involved in changes in GB contractility that occur during aging. Cytoplasmic Ca2+ concentrations ([Ca2+](i)) and the contractile force of guinea pig GB muscle strips were simultaneously measured using fura-2 and force-displacement transducers. The binding ability of the Ca2+ channel antagonist and GB muscle compliance were also examined. The COOH-terminal octapeptide of cholecystokinin (CCK-8) evoked a dose- dependent increase in force and [Ca2+](i). Changes of [Ca2+](i) and contractile force of muscle strips in response to CCK-8 were significantly greater in young (2 mo old) compared with mature and aged (12 and 24 mo old) guinea pigs (changes in [Ca2+](i), ED50: 46.1 nM at 2 mo, 6.1 μM at 12 mo, and 2.8 mM at 24 mo; changes of contractile force, ED50: 24.8 μM at 2 mo, 2.1 mM at 12 mo, and 357 mM at 24 mo). However, the magnitude of the contraction at each percent change in [Ca2+](i) was actually similar in young and aged guinea pigs. In a Ca2+-free buffer, the responses of [Ca2+](i) and force to CCK-8 in both young and aged GB muscles decreased, but those were still dose and age dependent. Binding ability of the Ca2+ channel antagonist did not differ in the young and aged groups, but the compliance of the GB muscle strip decreased with aging. These results suggest that both a reduced mobilization of intracellular Ca2+ and a decreased muscle compliance are responsible, at least in part, for age-related reduced contraction of guinea pig GB in response to CCK.

    Original languageEnglish (US)
    Pages (from-to)G624-G629
    JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
    Volume264
    Issue number4 27-4
    StatePublished - May 3 1993

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    Keywords

    • aging
    • antagonist
    • calcium channel
    • compliance
    • fura-2
    • motility
    • tension

    ASJC Scopus subject areas

    • Physiology
    • Hepatology
    • Gastroenterology
    • Physiology (medical)

    Cite this

    Ishizuka, J., Murakami, M., Nichols, G. A., Cooper, C. W., Greeley, G. H., & Thompson, J. C. (1993). Age-related changes in gallbladder contractility and cytoplasmic Ca2+ concentration in the guinea pig. American Journal of Physiology - Gastrointestinal and Liver Physiology, 264(4 27-4), G624-G629.