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
*ﾊ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ﾊ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 (3ｫﾊ10^-7ﾊM) did not affect these oscillations. Phorbol 12,13-dibutyrate (10^-7ﾊ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 (3ｫﾊ10^-5ﾊM) also significantly increased the frequency of Ca²⁺ oscillations. Acetylcholine (10^-8ﾊ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ﾊ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ﾊC, Ca²⁺ store, Ileal smooth muscle