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 2.3×10−10 M, freely fed rats 2.5×10−10 M, omeprazole‐treated rats 8.7×10−10 M. 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
在清醒大鼠中,通过胃下黏膜微透析监测ECL细胞中组胺的释放。ECL细胞已知在促胃液素的调控下工作,本研究的目的是探讨它们对短期(12小时)和长期(28天)高促胃液素血症的< jats:italic>in situ反应,该高促胃液素血症通过质子泵抑制剂奥美拉唑的治疗诱导。高促胃液素血症迅速提高了微透析液中的组胺浓度。该效应被CCK2受体阻滞剂(YF476)所阻止。在奥美拉唑治疗的第7天,微透析液中的组胺浓度达到峰值,比治疗前高5倍。随后(14天和28天),释放的组胺减少。通过胃泌素输注(4小时)在禁食大鼠、自由摄食大鼠以及奥美拉唑治疗一周的大鼠中,微透析液中的组胺浓度呈现出剂量依赖性的上升。然而,禁食和自由摄食的大鼠对低剂量胃泌素有反应,而奥美拉唑治疗的大鼠则需要大剂量胃泌素才能产生反应。当释放的组胺量与血清胃泌素浓度相关时,可以计算出以下EC50值:禁食大鼠2.3×10−10 P,自由摄食大鼠2.5×10−10 P,奥美拉唑治疗的大鼠8.7×10−10 P。三个组的最大组胺反应分别为18.4 pmol 4 h-1 ±0.8、21.9 pmol 4 h-1 ±1.2和68.0 pmol 4 h-1 ±3.5。结果表明,暴露于高胃泌素浓度一周的ECL细胞,其受体-配体结合亲和力发生了从高到低的转变。显然,ECL细胞的CCK2受体在配体结合亲和力方面经历了动态变化。 英国药理学杂志(2001)133, 37–42;doi: 10.1038/sj.bjp.0704037