Hirokawa Masahiko, Furukawa Osamu, Guth Paul H, Engel Eli, Kaunitz Jonathan D
Center for Ulcer Research and Education: Digestive Diseases Research Center, Los Angeles 90073, USA.
Am J Physiol Gastrointest Liver Physiol. 2004 Jun;286(6):G891-8. doi: 10.1152/ajpgi.00458.2003. Epub 2004 Feb 5.
Luminal exposure to concentrated acid, the most accepted physiological stimulus for duodenal bicarbonate secretion (DBS), cannot be used with in vitro preparations due to potential tissue damage. We thus examined whether exposure to PGE(2), a well-characterized physiological duodenal secretagogue, could mimic the effects of acid perfusion. DBS was measured in C57/BL mice by pH-stat/back-titration and measurement of total dissolved CO(2) concentration (CO(2)). Anion transport inhibitor DIDS, anion channel inhibitor 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), carbonic anhydrase inhibitor methazolamide, and nonselective cyclooxygenase inhibitor indomethacin were used to inhibit separate components of HCO(3)(-) secretory pathway. Baseline DBS was not altered by exposure to methazolamide (0.1 mM) but was slightly reduced by DIDS (0.5 mM). DBS and CO(2) increased after acid and PGE(2) exposure. DIDS (0.5 mM) and NPPB (0.2 mM) abolished acid-induced DBS increase. Methazolamide (0.1 mM) and DIDS inhibited acid-induced CO(2) increase. DIDS, NPPB, or methazolamide had little effect on DBS in response to high concentration PGE(2) (100 microg/ml). Low concentration PGE(2) (1 microg/ml) increased DBS that was inhibited by DIDS, NPPB, and methazolamide. Pretreatment with indomethacin (5 mg/kg) inhibited DBS induced by acid exposure but not by PGE(2). High-dose PGE(2) substantially increases DBS by a mechanism that appears to be different than secretory response to luminal acid perfusion. Secretory response to low-dose PGE(2), at least in terms of inhibitor profile, closely resembles secretion in response to perfusion of physiological acid concentrations and may be a useful stimulus for in vitro study of DBS in isolated mouse duodenum.
腔内暴露于浓酸是十二指肠碳酸氢盐分泌（DBS）最公认的生理刺激因素，但由于可能造成组织损伤，不能用于体外实验。因此，我们研究了暴露于前列腺素E2（PGE2）（一种已明确特征的生理性十二指肠促分泌素）是否能模拟酸灌注的作用。通过pH计/回滴法及测量总溶解二氧化碳浓度（[CO2]t）来测定C57/BL小鼠的DBS。使用阴离子转运抑制剂二氢吲哚-2,2'-二磺酸（DIDS）、阴离子通道抑制剂5-硝基-2-（3-苯丙基氨基）苯甲酸（NPPB）、碳酸酐酶抑制剂甲唑酰胺以及非选择性环氧化酶抑制剂吲哚美辛来抑制HCO3-分泌途径的不同组分。暴露于甲唑酰胺（0.1 mM）对基线DBS无影响，但DIDS（0.5 mM）使其略有降低。酸和PGE2暴露后，DBS和[CO2]t升高。DIDS（0.5 mM）和NPPB（0.2 mM）消除了酸诱导的DBS升高。甲唑酰胺（0.1 mM）和DIDS抑制了酸诱导的[CO2]t升高。DIDS、NPPB或甲唑酰胺对高浓度PGE2（100μg/ml）刺激的DBS影响很小。低浓度PGE2（1μg/ml）使DBS升高，这被DIDS、NPPB和甲唑酰胺抑制。吲哚美辛（5 mg/kg）预处理抑制了酸暴露诱导的DBS，但不抑制PGE2诱导的DBS。高剂量PGE2通过一种似乎不同于腔内酸灌注分泌反应的机制显著增加DBS。低剂量PGE2的分泌反应，至少就抑制剂谱而言，与生理酸浓度灌注的分泌反应非常相似，可能是体外研究分离的小鼠十二指肠DBS的有用刺激因素。
