Jpn. J. Pharmacol. 82 (4), 317-325 (2000)

Characteristics of Ca2+ Oscillations in Ileal Longitudinal Muscle Cells of Guinea Pig

Mitsutoshi Satoh, Issei Takayanagi and Katsuo Koike*

Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences,
Miyama 2-2-1, Funabashi, Chiba 274-8510, Japan
*╩To whom correspondence should be addressed.

Abstract: We studied the mechanisms and characteristics of the spontaneously evoked intracellular Ca2+ changes (Ca2+ oscillations) in ileal longitudinal smooth muscle from guinea pig. Two-dimensional images of Ca2+ oscillations were obtained at 33-ms intervals with a Ca2+-sensitive fluorescence probe, fluo-3 using the intensified CCD camera. Nicardipine (10-7╩M) significantly decreased the maximum level of fluorescence intensity of the Ca2+ oscillations, inhibited the frequency of the oscillations and tended to decrease the basal level of fluorescence intensity. However, tetrodotoxin (3ź╩10-7╩M) did not affect these oscillations. Phorbol 12,13-dibutyrate (10-7╩M) significantly increased the maximum level of fluorescence intensity and the frequency of Ca2+ oscillations, and it changed them to steady and chronometric Ca2+ oscillations. Cyclopiazonic acid (3ź╩10-5╩M) also significantly increased the frequency of Ca2+ oscillations. Acetylcholine (10-8╩M) increased the basal and maximum level of fluorescence intensity and the frequency of Ca2+ oscillations, and accelerated their onset. The increase of basal level of fluorescence intensity was then decreased by cyclopiazonic acid treatment. These results suggest that the augmentation of Ca2+ oscillations is mainly due to the activation of L-type Ca2+ channels, which is modulated by protein kinase╩C, and that the emptying of intracellular Ca2+ stores may activate the Ca2+ oscillations mediated through the increase of Ca2+ influx in ileal smooth muscle of guinea pig.

Keywords: Ca2+ oscillation, Ca2+ channel, Protein kinase╩C, Ca2+ store, Ileal smooth muscle

Copyrightę The Japanese Pharmacological Society 2000

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