Abstract
The final steps of exocytosis are consisted of three steps, docking, priming, and fusion, in which the priming step is maintained by ATP. We examined the effects of Cl−-free solution on the priming step.The isolated antral mucous cells were obtained by a collagenase treatment, and observed using video-microscopy. In Cl−-free solution, Cl− was replaced with NO3−.Acetylcholine (ACh 1 μM) increases the frequency of exocytosis ; an initial phase followed by a sustained phase. The Cl−-free solution enhanced the initial peak frequency of ACh-evoked exocytosis approximately 4 fold respectively.To examine effects of Cl−-free solution on the priming step, intracellular ATP was depleted by anoxia (aerated with N2 100%) or dinitrophenol (DNP 100 μM). Depletion of ATP eliminated the initial phase of ACh-evoked exocytotic events. After ATP depletion, Cl−-free solution did not evoke any initial phase.However, when cells were first perfused with Cl−-free solution, and then ATP was depleted, ACh induced an initial phase. Moreover, cells were first stimulated with ACh, which depelets the primed granules, and after a short interval (9min), cells were stimulated with ACh again. The initial phase was induced by the second ACh stimulation during perfusion with Cl−-free solution, while it was not during perfusion with the control solution.Based on the observation, Cl−-free solution increases number of the primed granules, which enhances ACh-evoked exocytotic events in antral mucous cells. [J Physiol Sci. 2006;56 Suppl:S110]
