Mobilization of rat stomach ECL-cell histamine in response to short- or long-term treatment with omeprazole and/or YF 476 studied by gastric submucosal microdialysis in conscious rats
作者:T Konagaya、M Bernsand、P Norlén、R Håkanson
DOI:10.1038/sj.bjp.0704037
日期:2001.5
Mobilization of histamine from the ECL cells was monitored by gastric submucosal microdialysis in conscious rats. The ECL cells are known to operate under gastrin control and the purpose of the present study was to examine their in situ response to short‐term (12 h) as well as long‐term (28 days) hypergastrinaemia, induced by treatment with the proton pump inhibitor omeprazole.Hypergastrinaemia promptly raised the histamine concentration in the microdialysate. The effect was prevented by CCK2 receptor blockade (YF476). On day 7 of omeprazole treatment the microdialysate histamine concentration reached a peak, five times higher than before treatment. Subsequently (14 and 28 days), less histamine was mobilized.Gastrin infusion (4 h) raised the microdialysate histamine concentration in a dose‐dependent manner in fasted rats and freely fed rats and in rats treated with omeprazole for a week. However, while fasted and fed rats responded to low doses of gastrin, the omeprazole‐treated rats required large doses of gastrin to respond.When the amount of histamine mobilized was related to the serum gastrin concentration the following EC50 values could be calculated: fasted rats 2.3×10−10M, freely fed rats 2.5×10−10M, omeprazole‐treated rats 8.7×10−10M. The maximal histamine responses in the three groups were 18.4 pmol 4 h−1±0.8, 21.9 pmol 4 h−1±1.2 and 68.0 pmol 4 h−1±3.5, respectively.The results suggest that ECL cells, exposed to a high gastrin concentration for a week, respond with a shift in the receptor‐ligand binding affinity from high to low. Apparently, CCK2 receptors of the ECL cells are subject to dynamic changes with respect to ligand‐binding affinity.British Journal of Pharmacology (2001) 133, 37–42; doi:10.1038/sj.bjp.0704037
The Chameleonic Nature of the Nitro Group Applied to a Base-Promoted Cascade Reaction To Afford Indane-Fused Dihydrofurans
作者:Howard Díaz-Salazar、Juan Carlos Rodríguez-Colín、Josué Vazquez-Chavez、Marcos Hernández-Rodríguez
DOI:10.1021/acs.joc.3c00132
日期:2023.7.7
Michael/Conia-ene/SN2 cascadereaction for the synthesis of Indane-fused dihydrofurans from 1,3-dicarbonyl compounds and 2-alkynylnitrostyrenes promoted by potassium carbonate in DMSO at room temperature. In this reaction, the nitro group has a chameleonic role, first as an electron-withdrawing group for the Michael addition, then the nitronate behaves as a nucleophile, and finally, the allylic nitro acts as a
我们公开了在室温下在DMSO中碳酸钾促进下由1,3-二羰基化合物和2-炔基硝基苯乙烯合成茚满稠合二氢呋喃的Michael/Conia-ene/S N 2 级联反应。在该反应中,硝基具有变色作用,首先作为迈克尔加成的吸电子基团,然后硝基充当亲核试剂,最后,烯丙基硝基充当离去基团。该产品以单一非对映异构体形式获得,其中 1,3-酮酯含量高达 82%,1,3-二酮含量高达 58%。此外,反应机理的 DFT 计算解释了硝基化合物在烯醇化物上化学选择性加成到未活化的三键上,烯醇化物的加成是高度吸热的。