Regulation of gastric acid secretion by PKB/Akt2.
Pharmacological inhibition of phosphoinositol 3 kinase (PI3K) and partial deficiency of phosphoinositide dependent kinase PDK1 have previously been shown to enhance basal gastric acid secretion. PI3K/PDK1 dependent signaling involves activation of protein kinase B/Akt, which may thus be similarly involved in the regulation of gastric acid secretion. To test that hypothesis, gastric acid secretion was determined in isolated glands from gene targeted mice lacking functional Akt2 (akt2(-/-)) or from their wild type littermates (akt2(+/+)). According to BCECF-fluorescence cytosolic pH in isolated gastric glands was similar in akt2(-/-) and akt2(+/+) mice. Na(+)-independent pH recovery (DeltapH/min) following an ammonium pulse, a measure of H(+)/K(+) ATPase activity, was, however, significantly faster in akt2(-/-) than in akt2(+/+) mice. In both genotypes, DeltapH/min was virtually abolished by H(+)/K(+) ATPase inhibitor omeprazole (100 muM). Increase of extracellular K(+) concentrations to 35 mM (replacing Na(+)) increased DeltapH/min to a significantly larger extent in akt2(+/+) than in akt2(-/-) mice and dissipated the differences between the genotypes. Similarly, treatment with 5 muM forskolin enhanced DeltapH/min significantly only in akt2(+/+) mice and abolished the differences between the genotypes. Conversely, protein kinase A inhibitor H89 (50 nM) decreased DeltapH/min to similarly low values in both genotypes. In conclusion, Akt2 suppresses gastric acid secretion and contributes to or even accounts for the inhibition of gastric acid secretion by PI3K.
Rotte
Anand
A
Department of Physiology, University of Tübingen, D-72076 Tübingen, Germany.
Pasham
Venkanna
V
Bhandaru
Madhuri
M
Eichenmüller
Melanie
M
Yang
Wenting
W
Qadri
Syed M
SM
Kempe
Daniela S
DS
Puchchakayala
Goverdhan
G
Pearce
David
D
Birnbaum
Morris J
MJ
Lang
Florian
F
D000818:Animals; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D005744:Gastric Acid / Q000378:metabolism*; D005753:Gastric Mucosa / Q000378:metabolism; D017353:Gene Deletion; D006863:Hydrogen-Ion Concentration; D051657:KCNQ1 Potassium Channel / Q000378:metabolism; D008297:Male; D051379:Mice; D010295:Parietal Cells, Gastric / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*
D051657:KCNQ1 Potassium Channel; C496910:Kcnq1 protein, mouse; D000242:Cyclic AMP; D051057:Proto-Oncogene Proteins c-akt; D011188:Potassium