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标题：Duodenal acidity “sensing” but not epithelial HCO3− supply is critically dependent on carbonic anhydrase II expression
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作者：Markus Sjöblom ; Anurag Kumar Singh ; Wen Zheng 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：31
页码：13094-13099
DOI：10.1073/pnas.0901488106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Carbonic anhydrase (CA) is strongly expressed in the duodenum and has been implicated in a variety of physiological functions including enterocyte HCO3- supply for secretion and the "sensing" of luminal acid and CO2. Here, we report the physiological role of the intracellular CAII isoform involvement in acid-, PGE2, and forskolin-induced murine duodenal bicarbonate secretion (DBS) in vivo. CAII-deficient and WT littermates were studied in vivo during isoflurane anesthesia. An approximate 10-mm segment of the proximal duodenum with intact blood supply was perfused under different experimental conditions and DBS was titrated by pH immediately. Two-photon confocal microscopy using the pH-sensitive dye SNARF-1F was used to assess duodenocyte pHi in vivo. After correction of systemic acidosis by infusion of isotonic Na2CO3, basal DBS was not significantly different in CAII-deficient mice and WT littermates. The duodenal bicarbonate secretory response to acid was almost abolished in CAII-deficient mice, but normal to forskolin- or 16,16-dimethyl PGE2 stimulation. The complete inhibition of tissue CAs by luminal methazolamide and i.v. acetazolamide completely blocked the response to acid, but did not significantly alter the response to forskolin. While duodenocytes acidified upon luminal perfusion with acid, no significant pHi change occurred in CAII-deficient duodenum in vivo. The results suggest that CA II is important for duodenocyte acidification by low luminal pH and for eliciting the acid-mediated HCO3- secretory response, but is not important in the generation of the secreted HCO3- ions.
关键词：bicarbonate secretion ; duodenal mucosal protection ; duodenal ulcers ; gastrointestinal phenotype ; gastric acid