Gastric acid secretion in aquaporin-4 knockout mice.
The aquaporin-4 (AQP4) water channel has been proposed to play a role in gastric acid secretion. Immunocytochemistry using anti-AQP4 antibodies showed strong AQP4 protein expression at the basolateral membrane of gastric parietal cells in wild-type (+/+) mice. AQP4 involvement in gastric acid secretion was studied using transgenic null (-/-) mice deficient in AQP4 protein. -/- Mice had grossly normal growth and appearance and showed no differences in gastric morphology by light microscopy. Gastric acid secretion was measured in anesthetized mice in which the stomach was luminally perfused (0. 3 ml/min) with 0.9% NaCl containing [(14)C]polyethylene glycol ([(14)C]PEG) as a volume marker. Collected effluent was assayed for titratable acid content and [(14)C]PEG radioactivity. After 45-min baseline perfusion, acid secretion was stimulated by pentagastrin (200 microg. kg(-1). h(-1) iv) for 1 h or histamine (0.23 mg/kg iv) + intraluminal carbachol (20 mg/l). Baseline gastric acid secretion (means +/- SE, n = 25) was 0.06 +/- 0.03 and 0.03 +/- 0.02 microeq/15 min in +/+ and -/- mice, respectively. Pentagastrin-stimulated acid secretion was 0.59 +/- 0.14 and 0.70 +/- 0.15 microeq/15 min in +/+ and -/- mice, respectively. Histamine plus carbachol-stimulated acid secretion was 7.0 +/- 1.9 and 8.0 +/- 1.8 microeq/15 min in +/+ and -/- mice, respectively. In addition, AQP4 deletion did not affect gastric fluid secretion, gastric pH, or fasting serum gastrin concentrations. These results provide direct evidence against a role of AQP4 in gastric acid secretion.
Department of Surgery, Stanford University, CA 94305-5655, USA.
K S
KS
Wang
A R
AR
Komar
T
T
Ma
F
F
Filiz
J
J
McLeroy
K
K
Hoda
A S
AS
Verkman
J A
JA
Bastidas
D000818:Animals; D000906:Antibodies; D051401:Aquaporin 4; D020346:Aquaporins / Q000032:analysis / Q000235:genetics* / Q000276:immunology; D002217:Carbachol / Q000494:pharmacology; D018678:Cholinergic Agents / Q000494:pharmacology; D005744:Gastric Acid / Q000378:metabolism*; D005753:Gastric Mucosa / Q000378:metabolism*; D005755:Gastrins / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D017506:H(+)-K(+)-Exchanging ATPase / Q000235:genetics; D006632:Histamine / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D051379:Mice; D008822:Mice, Transgenic; D010295:Parietal Cells, Gastric / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology; D010418:Pentagastrin / Q000097:blood / Q000494:pharmacology; D013270:Stomach / Q000737:chemistry / Q000166:cytology; D014867:Water / Q000378:metabolism
D000906:Antibodies; C496031:Aqp4 protein, mouse; D051401:Aquaporin 4; D020346:Aquaporins; D018678:Cholinergic Agents; D005755:Gastrins; D014867:Water; D006632:Histamine; D002217:Carbachol; D017506:H(+)-K(+)-Exchanging ATPase; D010418:Pentagastrin