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

摘要

References(41) 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(10-7M)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(3×10-7M)did not affect these oscillations.Phorbol 12, 13-dibutyrate(10-7M)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(3×10-5M)also significantly increased the frequency of Ca2+ oscillations.Acetylcholine(10-8M)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.