Kento Takahashi

Stimulation of duodenal HCO3− secretion by hydrogen sulphide in rats: relation to prostaglandins, nitric oxide and sensory neurones

Aim:  We examined the effect of H2S on duodenal HCO3− secretion in rats and investigated the mechanism involved in this response.

Phosphodiesterase Isozymes Involved in Regulation of HCO3- Secretion in Isolated Mouse Stomach in Vitro

(±)-(E)-4-Ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide] (NOR-3), a nitric-oxide (NO) donor, is known to increase \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{HCO}_{3}^{-}\) \end{document} secretion in rat stomachs, intracellularly mediated by cGMP; yet, there is no information about the phosphodiesterase (PDE) isozyme involved in this process. We examined the effects of various isozyme-selective PDE inhibitors on the secretion of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{HCO}_{3}^{-}\) \end{document} in the mouse stomach in vitro and the type(s) of PDE isozymes involved in the response to NO. The gastric mucosa of DDY mice was stripped of the muscle layer and mounted on an Ussing chamber. \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{HCO}_{3}^{-}\) \end{document} secretion was measured at pH 7.0 using a pH-stat method and by adding 2 mM HCl. NOR-3, 8-bromoguanosine 3′,5′-cyclic monophosphate (8-Br-cGMP), and various PDE inhibitors were added to the serosal side. Vinpocetine (PDE1 inhibitor) or zaprinast (PDE5 inhibitor) was also added serosally 30 min before NOR-3 or 8-Br-cGMP. Both NOR-3 and 8-Br-cGMP stimulated \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{HCO}_{3}^{-}\) \end{document} secretion in a dose-dependent manner, and the response to NOR-3 was significantly inhibited by methylene blue. Likewise, the secretion induced by NOR-3 or 8-Br-cGMP was significantly attenuated by 6-((2S,3S)-3-(4-chloro-2-methylphenylsulfonylaminomethyl)-bicyclo(2.2.2)octan-2-yl)-5Z-hexenoic acid (ONO-8711), the PGE receptor (EP)1 antagonist, as well as indomethacin and potentiated by both vinpocetine and zaprinast at doses that had no effect by themselves on the basal secretion, whereas other subtype-selective PDE inhibitors had no effect. NOR-3 increased the mucosal PGE2 content in a methylene blue-inhibitable manner. These results suggest that NO stimulates gastric \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{HCO}_{3}^{-}\) \end{document} secretion mediated intracellularly by cGMP and modified by both PDE1 and PDE5, and this response is finally mediated by endogenous PGE2 via the activation of EP1 receptors.

H2S-induced HCO3− secretion in the rat stomach – Involvement of nitric oxide, prostaglandins, and capsaicin-sensitive sensory neurons

Hydrogen sulfide (H2S) is known to be an important gaseous mediator that affects various functions under physiological and pathological conditions. We examined the effects of NaHS, a H2S donor, on HCO3(-) secretion in rat stomachs and investigated the mechanism involved in this response. Under urethane anesthesia, rat stomachs were mounted on an ex vivo chamber and perfused with saline. Acid secretion had been inhibited by omeprazole. The secretion of HCO3(-) was measured at pH 7.0 using a pH-stat method and by the addition of 10 mM HCl. NaHS (0.5-10 mM) was perfused in the stomach for 5 min. Indomethacin or L-NAME was administered s.c. before NaHS treatment, while glibenclamide (a KATP channel blocker), ONO-8711 (an EP1 antagonist), or propargylglycine (a cystathionine γ-lyase inhibitor) was given i.p. before. The mucosal perfusion of NaHS dose-dependently increased the secretion of HCO3(-), and this effect was significantly attenuated by indomethacin, L-NAME, and sensory deafferentation, but not by glibenclamide or ONO-8711. The luminal output of nitric oxide, but not the mucosal production of prostaglandin E2, was increased by the perfusion of NaHS. Mucosal acidification stimulated HCO3(-) secretion, and this response was inhibited by sensory deafferentation, indomethacin, L-NAME, and ONO-8711, but not by propargylglycine. These results suggested that H2S increased HCO3(-) secretion in the stomach, and this effect was mediated by capsaicin-sensitive afferent neurons and dependent on nitric oxide and prostaglandins, but not ATP-sensitive K(+) channels. Further study is needed to define the role of endogenous H2S in the mechanism underlying acid-induced gastric HCO3(-) secretion.

401 Lubiprostone Stimulates HCO3- Secretion in Isolated Mouse Stomachs In Vitro Through Activation of Prostaglandin EP1 Receptors

modification of intestinal epithelial architecture including villus blunting (WT: 627.03 ± 53.21 vs IL13Tg: 462.57 ± 47.66 μm, p < 0.0001, n=34) , goblet cell hyperplasia (WT: 0.063 ± 0.024 vs IL13Tg: 0.123 ± 0.029, p<0.0001, n=22), increased epithelial proliferation and migration (villus / crypt, Wt: 4.977 ± 0.873 vs IL-13Tg: 3.382 ± 0.680, p<0.0001, n= 25). Modification of epithelial architecture was associated with increased Clsecretion (TER: Wt: 153.333 ± 16.449 vs IL13Tg: 92.004 ± 12.671Ω/cm2, p=0.0014, n=3). Pharmacological analyses In Vitro and In Vivo determined IL-13 stimulated Clsecretion to be driven by CFTR Clchannel activity. IL-13 mediated dysregulation of epithelial architecture and barrier function was dependent on IL-13Rα1 and not IL-13Rα2. These observations demonstrate a central role for IL-13 in the regulation of intestinal epithelial cell function and suggest that IL-13 may have an important role in food allergy.

W1542 Effect of Carbon Monoxide On HCO3- Secretion in Rat Stomachs: Involvement of Heme Oxygenase in Regulation of Gastric HCO3- Response

G A A b st ra ct s -/mice to wild type mice to determine if zinc works via the receptor or by direct interactions within the cytosol. Material and methods: Wild type and CaSR-deficient mice were fasted for 12-18 hours prior to sacrifice to ensure a consistent minimum of gastric acid secretion. Single gastric glands were hand-dissected from the corpus of the stomach. After incubation with the pH-sensitive dye, BCECF glands were transferred to a coverslip precoated with a biological cell adhesive, mounted in a chamber maintained at 37° and then imaged on a real time fluorescence digital system. For reproducible acidification, glands were exposed to a Na+-free NH4Cl prepulse and a 0 mM Na+ solution. Following acid loading and Na+removal, acid extrusion was monitored as rate of intracellular alkalinization. To examine proton extrusion by H+,K+-ATPase and to preclude contribution of Na+/H+ exchange, Na+free conditions were chosen. The rate of pH recovery, representing H+,K+-ATPase activity, was calculated as ΔpHi/Δt, using a high-K+/Nigericin calibration technique. In wild type mice Histamine or a potent calcimimetic activator of the CaSR, were used to stimulate acid secretion. In CaSR-deficient mice Histamine alone was used. In a subsequent series of experiments Zinc was added. Results: In the presence of functional CaSR the inhibitory effect of Zinc on gastric acid secretion was significantly higher than that seen in CaSRdeficient mice, suggesting the primary pathway for zinc action is at the level of the CaSR. Conclusion: This study shows the predominant role of the CaSR in Zinc-mediated inhibition of gastric acid secretion. Additionally this study suggests the importance of dietary zinc to modulate acid production. Failure to have sufficient zinc in the diet would result in reduced serum levels of zinc. This reduction in zinc could lead to an enhanced CaSR function and subsequent gastric acid hypersecretion even in the absence of hormonal or neuronal stimulation.

W1715 Effect of Carbon Monoxide/Heme Oxygenase On Duodenal HCO3- Secretion in Rats

Background/Aims: Carbon monoxide (CO) with free iron and biliverdin are generated from degradation of heme catalyzed by constitutive heme oxygenase (HO-2) and inducible HO1. Particularly, HO-1 is recognized as the stress protein, which is up-regulated by various stresses and exerts a protective action against tissue injury. By the way, HCO3secretion is one of protective mechanisms in the duodenum against acid stress. However, no information is available concerning the relation of HO-1/CO with HCO3secretion. In the present study, we examined the effect of a CO donor on HCO3secretion in the rat duodenum and investigated whether HO-1 is involved in the physiological regulation of this secretion. Methods: Male SD rats were used after 18 h fasting. Under urethane anesthesia, a proximal duodenal loop was perfused with saline, and HCO3secretion was measured at pH 7.0 using a pH-stat method. CORM-2 (a CO donor; 0.5-2 mM), biliverdin (10 mg/ml) or ruthenium (III) chloride (Ru; a negative control; 5 mM) was applied to the loop for 5 min. Mucosal acidification was performed by exposing the loop to 10 mM HCl for 10 min. Acetazolamide (an inhibitor of CA), indomethacin or L-NAME (a NOS inhibitor) was given SC 1 h or 3 h before the administration of agonists, while SnPP (an inhibitor of HO), CuPP (a negative inhibitor) or hemin was given IP 1 h before. Expression of HO protein was examined by western blot. Results: Topical application of CORM-2 significantly increased duodenal HCO3secretion in a concentration dependent manner, while neither Ru nor biliverdin have any effect. The stimulatory effect of CORM-2 was significantly attenuated by indoemthacin and acetazolamide but not L-NAME. The secretion of HCO3was increased by acidification of the mucosa, in an indomethacin-inhibitable manner. The acid-induced HCO3response was also markedly inhibited by SnPP but not CuPP. Furthermore, the inhibitory effect of SnPP was significantly reversed by the pretreatment with hemin. On the other hand, perfusion of the duodenal loop with 100 mM HCl for 2 h caused hemorrhagic lesions, and this response was significantly worsened by the prior administration of SnPP as well as indomethacin. In addition, the expression of HO-1 but not HO-2 protein was markedly up-regulated in the duodenum following acid perfusion for 4 h. Conclusions: These results suggest that CO stimulates HCO3secretion in the duodenum, and this effect is mediated by endogenous PGs and partly dependent on CO2 generated from the reaction of CO with O2. It is assumed that HO-1 plays an important role in maintaining the integrity of the duodenal mucosa when the tissue is exposed to acid stress.