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

Abstract

(Ϯ)-(E)-4-Ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide](NOR-3), a nitric-oxide (NO) donor, is known to increase HCO 3 Ϫ 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 HCO 3 Ϫ 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. HCO 3 Ϫ secretion was measured at pH 7.0 using a pH-stat method and by adding 2 mM HCl. NOR-3, 8-bromoguanosine 3Ј,5Ј-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 HCO 3 Ϫ secretion in a dosedependent 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 PGE 2 content in a methylene blueinhibitable manner. These results suggest that NO stimulates gastric HCO 3 Ϫ secretion mediated intracellularly by cGMP and modified by both PDE1 and PDE5, and this response is finally mediated by endogenous PGE 2 via the activation of EP1 receptors.

Prophylactic and therapeutic benefits of COX-2 inhibitor on motility dysfunction in bowel obstruction: roles of PGE2 and EP receptors

“…The muscle strips were incubated for 24 h with vehicle control (DMSO), and the specific antagonists to EP1 (SC-52342, Enzo, Plymouth Meeting, PA), EP1/EP2 (AH6809, Enzo), EP3 (L-798106, Tocris Bioscience, Ellisville, MO) and EP4 (ONO-AE 3-208, Haoyuan Chemexpress, Shanghai, China), separately. The concentration of 10 Ϫ5 M was chosen for all the antagonists because this was found effective in blocking respective EP receptor subtypes (4,18,32,48). Incubation with EP2 or EP4 antagonists did not significantly change colonic circular muscle contractility in sham control tissue (Fig.…”

Importance of Ca2+ in gastric epithelial restitution—new views revealed by real-time in vivo measurements

“…The gastric mucosal bicarbonate secretion is mediated by cGMP and Ca 2+ [60,61]. it has been shown that cGMP-induced bicarbonate secretion is mediated by COX/PGE 2 /EP1 receptor [62], so based on known signaling by this receptor, Ca 2+ is likely to be the most downstream messenger to elicit receptor actions. In contrast, evidence from cultured cells suggests that neither cAMP nor cGMP plays any role in gastric epithelial cell migration [21,63].…”