Roles of AQP5/AQP5-G103D in carbamylcholine-induced volume decrease and in reduction of the activation energy for water transport by rat parotid acinar cells.
In order to assess the contribution of the water channel aquaporin-5 (AQP5) to water transport by salivary gland acinar cells, we measured the cell volume and activation energy (E (a)) of diffusive water permeability in isolated parotid acinar cells obtained from AQP5-G103D mutant and their wild-type rats. Immunohistochemistry showed that there was no change induced by carbamylcholine (CCh; 1 μM) in the AQP5 detected in the acinar cells in the wild-type rat. Acinar cells from mutant rats, producing low levels of AQP5 in the apical membrane, showed a minimal increase in the AQP5 due to the CCh. In the wild-type rat, CCh caused a transient swelling of the acinus, followed by a rapid agonist-induced cell shrinkage, reaching a plateau at 30 s. In the mutant rat, the acinus did not swell by CCh challenge, and the agonist-induced cell shrinkage was delayed by 8 s, reaching a transient minimum at around 1 min, and recovered spontaneously even though CCh was persistently present. In the unstimulated wild-type acinar cells, E (a) was 3.4 ± 0.6 kcal mol(-1) and showed no detectable change after CCh stimulation. In the unstimulated mutant acinar cells, high E (a) value (5.9 ± 0.1 kcal mol(-1)) was detected and showed a minimal decrease after CCh stimulation (5.0 ± 0.3 kcal mol(-1)). These results suggested that AQP5 was the main pathway for water transport in the acinar cells and that it was responsible for the rapid agonist-induced acinar cell shrinkage and also necessary to keep the acinar cell volume reduced during the steady secretion in the wild-type rat.
Department of Regulatory Physiology, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu-machi, Shimotsuga-gun, Tochigi, 321-0293, Japan. k-satoh@dokkyomed.ac.jp
Keitaro
K
Satoh
Yoshiteru
Y
Seo
Shinsuke
S
Matsuo
Mileva Ratko
MR
Karabasil
Miwako
M
Matsuki-Fukushima
Takashi
T
Nakahari
Kazuo
K
Hosoi
D061354:Acinar Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D051402:Aquaporin 5 / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002463:Cell Membrane Permeability; D048429:Cell Size; D009154:Mutation; D010306:Parotid Gland / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D011922:Rats, Mutant Strains; D014867:Water / Q000378:metabolism*
C496040:Aqp5 protein, rat; D051402:Aquaporin 5; D014867:Water; D002217:Carbachol