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 language||English (US)|
|Journal||American Journal of Physiology - Gastrointestinal and Liver Physiology|
|Issue number||4 27-4|
|State||Published - May 3 1993|
- calcium channel
ASJC Scopus subject areas
- Physiology (medical)