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Role of extracellular Ca 2+ in acetylcholine‐induced repetitive Ca 2+ release in submandibular gland acinar cells of the rat
Author(s) -
Zhang W.,
Fukushi Y.,
Nishiyama A.,
Wada J.,
Kamimura N.,
Mio Y.,
Wakui M.
Publication year - 1996
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/(sici)1097-4652(199605)167:2<277::aid-jcp11>3.0.co;2-5
Subject(s) - extracellular , intracellular , biophysics , acetylcholine , chemistry , stimulation , medicine , endocrinology , biology , biochemistry
Acetylcholine (ACh) caused repetitive transient Cl − currents activated by intracellular Ca 2+ in single rat submandibular grand acinar cells. As the concentration of ACh increased the amplitude and the frequency of the transient Cl − currents increased. These responses occurred also in the absence of extracellular Ca 2+ but disappeared after several minutes. Repetitive transient Cl − currents were restored by readmission of Ca 2+ to the extracellular solution. The higher the concentration of extracellular Ca 2+ readmitted, the larger the amplitude of the transient Cl − currents. Ca 2+ entry through a store‐coupled pathway was detected by application of Ca 2+ to the extracellular solution during a brief cessation of stimulation with ACh. In these experiments too, the higher the concentration of Ca 2+ , the larger the transient Cl − currents activated by Ca 2+ released from the stores. The time course of decrease in total charge movements of repetitive transient responses to ACh with removal of extracellular Ca 2+ depended on a decrease in charge movements of each transient event rather than a decrease in frequency of the repetitive events. The decrease of charge movements of each transient event was due to a decrease in its amplitude rather than its duration. The results suggest that in this cell type an amplitude‐modulated mechanism is involved in repetitive Ca 2+ release and that Ca 2+ entry is essential to maintain the repetitive release of Ca 2+ . The results further suggest that the magnitude of Ca 2+ entry determines the number of unitary stores filled with Ca 2+ which can synchronously respond to ACh. © 1996 Wiley‐Liss, Inc.