Hostname: page-component-848d4c4894-v5vhk Total loading time: 0 Render date: 2024-06-30T13:40:38.424Z Has data issue: false hasContentIssue false

Accumulation of cAMP evoked by acetylcholine stimulation in rat submandibular acinar cells: observation of exocytosis, fluid secretion and [Ca2+]i

Published online by Cambridge University Press:  25 January 2001

Takashi Nakahari
Affiliation:
Department of Physiology and Department of Chemistry, Osaka Medical College, Takatsuki 569-8686, Japan
Sigenori Ito
Affiliation:
Department of Physiology and Department of Chemistry, Osaka Medical College, Takatsuki 569-8686, Japan
Hideyo Yoshida
Affiliation:
Department of Physiology and Department of Chemistry, Osaka Medical College, Takatsuki 569-8686, Japan
Eisuke Furuya
Affiliation:
Department of Physiology and Department of Chemistry, Osaka Medical College, Takatsuki 569-8686, Japan
Yusuke Imai
Affiliation:
Department of Physiology and Department of Chemistry, Osaka Medical College, Takatsuki 569-8686, Japan
Get access

Abstract

The effects of cAMP accumulation evoked by acetylcholine (ACh) stimulation were studied in rat submandibular acinar cells by observing the exocytotic events, swelling of intercellular canaliculi (IC) and intracellular Ca2+ concentration ([Ca2+]i), which were monitored using an optical microscope. ACh stimulation evoked transient increases followed by sustained increases in the frequency of exocytotic events and IC swelling, while isoproterenol (isoprenaline; IPR) stimulation evoked sustained increases in these parameters. BAPTA treatment reduced the frequency of exocytotic events evoked by 5 µM ACh in the absence of extracellular Ca2+, and further addition of Rp-cAMPS or H-89 (protein kinase A (PKA) inhibitors) eliminated the remaining ACh-evoked responses (50 %). Addition of PKA inhibitors in the presence of extracellular Ca2+ reduced the frequency of exocytotic events evoked by 500 µM ACh in non-BAPTA-loaded cells. However, IC swelling evoked by 5 µM ACh was not affected by addition of PKA inhibitors, and was eliminated in BAPTA-loaded cells perfused with Ca2+-free solution. These results indicate that the IC swelling is regulated by [Ca2+]i and the frequency of exocytotic events is regulated by both [Ca2+]i and [cAMP]i during ACh stimulation. Addition of H-89 inhibited the capacitative Ca2+ entry into ACh-stimulated acinar cells. Biochemical analysis revealed that ACh stimulation increased the cAMP content in perfused submandibular glands. These results indicate that ACh stimulates the accumulation of cAMP in submandibular acinar cells and that this accumulation of cAMP modulates Ca2+-regulated exocytosis.

Type
Research Article
Copyright
© The Physiological Society 2000

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)