Role of extracellular Ca2+ in acetylcholine-induced repetitive Ca2+ release in submandibular gland acinar cells of the rat

✍ Scribed by W. Zhang; Y. Fukushi; A. Nishiyama; J. Wada; N. Kamimura; Y. Mio; M. Wakui

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 859 KB
• Volume: 167
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/(sici)1097-4652(199605)167:2<277::aid-jcp11>3.0.co;2-5

✦ Synopsis

Acetylcholine (ACh) caused repetitive transient CI-currents activated by intracellular Caz+ in single rat submandibular grand acinar cells. As the concentration of ACh increased the amplitude and the frequency of the transient CI-currents increased. These responses occurred also in the absence of extracellular Caz+ but disappeared after several minutes. Repetitive transient CI-currents were restored by readmission of Ca" to the extracellular solution. The higher the concentration of extracellular Ca2+ readmitted, the larger the amplitude of the transient CI-currents. Caz+ entry through a store-coupled pathway was detected by application of Ca" to the extracellular solution during a brief cessation of stimulation with ACh. In these experiments too, the higher the concentration of Ca2+, the larger the transient CI-currents activated by Ca2+ released from the stores. The time course of decrease in total charge movements of repetitive transient responses to ACh with removal of extracellular Ca2' 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 Ca2+ release and that Ca2+ entry is essential to maintain the repetitive release of Caz+. The results further suggest that the magnitude of Ca2+ entry determines the number of unitary stores filled with Ca2+ which can synchronously respond to ACh.