Altered expression of aquaporin 4 and H⁺/K⁺‐ATPase in the stomachs of peptide YY (PYY) transgenic mice

Abstract

Background information. The hormone PYY (peptide YY), synthesized by endocrine cells in the pancreas, ileum, colon and stomach has widespread inhibitory effects on gastrointestinal and pancreatic fluid secretion. Transgenic mice expressing a viral oncoprotein under the control of the PYY gene 5 -flanking region develop well-differentiated colonic endocrine tumours producing mainly PYY and enteroglucagon. In the present study, we investigated the expression of AQP4 (aquaporin 4) water channel and H + /K + -ATPase in stomachs from both control and transgenic mice.Results. Semi-quantitative RT (reverse transcriptase)-PCR showed an increase in the AQP4 transcript compared with control mice. Quantitative Western-blot analysis of stomachs from control and transgenic mice confirmed a significant increase in the 30 kDa AQP4 protein in transgenic mice. In control mice, AQP4 is specifically expressed in the basolateral membrane of gastric parietal cells, located in the basal region of the fundic glands. This particular location suggests that parietal cells in the base region of gastric pits might have a major role in water transport when compared with the more superficial parietal cells. Interestingly, immunofluorescence studies on transgenic mice revealed that the quantitative increase of AQP4 expression was actually due to an increase in the number of AQP4-expressing epithelial cells rather than to a higher expression of AQP4 in parietal cells. In fact, immunofluorescence experiments using the specific antibody raised against the AE2 isoform of Cl − /HCO 3 − exchanger specifically expressed in parietal cells confirmed that the number of parietal cells was comparable in both PYY and control stomachs.Moreover, in transgenic mice, a parallel significant decrease in the expression of H + /K + -ATPase was observed, as revealed by RT-PCR, quantitative immunoblotting and immunofluorescence.Conclusions. In the present study, we demonstrate that the sustained inhibition of gastric secretion due to tumours producing PYY/enteroglucagon in transgenic mice is associated with an increase in AQP4 expression and a downregulation of H + /K + -ATPase in parietal cells that acquire the characteristics of basal parietal cells. The absence of H 2 receptors-mediated signalling due to the inhibition of histamine release from ECL (enterochromaffin-like) cells by PYY may be in part responsible for the observed increase in the number of parietal cells expressing AQP4.

Immunohistochemical localization of aquaporin 4 (AQP4) in the porcine gastrointestinal tract

“…Since the application of proton pump inhibitors evoking acid suppression substantially increased the number of fundic AQP4-expressing parietal cells in the mouse, the involvement of aquaporin in gastric secretory processes (acid secretion) has been postulated (Matsuzaki et al 2010). This is in line with previous findings noting a higher expression level of AQP4 in the stomach (due to increased number of AQP4-positive parietal cells) of peptide YY transgenic mice (Carmosino et al 2005).…”

Detection of PLC- From Testis of Rattus Argentiventer(RiceField Rat) Using RT-PCR and qRT-PCR

“…β-actin was used as a positive control in the study because of its stability and consistency throughout all tissue samples (Katz et al, 2012). Similar positive control was used in a previous study of aquaporin and H+/K+-ATPase expression in transgenic mice (Carmosino et al, 2005). This study also confirmed the results of Jaffar, et.…”

“…A specific primer with a pair nucleotide of PLCforward 5'-CATGTGAAACATATTTTTAAGGAAA-3' and PLCreverse 5'-ATCCCCAAATGTCACTCGGTCC-3' (Fujimoto et al, 2004) were used to amplify cDNA. β-actinforward 5'-GTTTGAGACCTTCAACACCC-3' and β-actin reverse 5'-CCAATGGTGATGACCTGGCC-3' as a control (Carmosino, 2005) served as a positive control in the amplification process. The mixture was then kept in the thermal cycler machine (Eppendorf, Germany) for denaturation process.…”

Endoscopic Analysis of Gastric Ulcer after One Week's Treatment with Omeprazole and Rabeprazole in Relation to CYP2C19 Genotype

“…Parietal cells are scattered along the gastric gland. When they migrate from their generating region to the base region of gastric gland during their life span, they gradually lose acid secretory activity [1][2][3]. Accumulation of rabeprazole (PPI, its pKa is about 5.0) in weakly acidic region is greater than those of other PPIs such as omeprazole, lansoprazole and pantoprazole (pKa around 4.0).…”