- 作者: Li Hsueh Tsai Yih-Jing Lee Jang-Yen Wu
- 作者服務機構: Department of Physiology, School of Medicine, Taipei Medical College, Taipei, Taiwan, ROC, Department of Biochemistry, Cell Biology and Molecular Biology, University of Kansas, Lawrence, Kans., USA
- 中文摘要: --
- 英文摘要: Excitatory amino acids(EAAs), in particular, L-aspartate(L-Asp) neurons and their processes, were localized inthe rat stomach using a immunohistochemical methodwith specific antibodies against either L-Asp or its syn-thesizing enzyme, aspartate aminotransferase (AAT).Myenteric ganglia and nerve bundles in the circular mus-cle and in the longitudinal muscle were found to be AAT-or L-Asp-positive. In addition, AAT- or L-Asp-positivecells were also found in the muscle layer and the deepmucosal layer. The distribution of AAT- or L-Asp-positivecells in both the mucosal and muscle layers was hetero-geneous in the stomach. In addition, L-Asp at 10 Mnegligibly influenced acid secretion in an everted prepa-ration of isolated rat stomach. However, according to ourresults, L-Asp markedly inhibited the histamine-stimulat-ed acid secretion, but not the oxotremorine- or the penta-gastrin-stimulated acid secretion. Furthermore, L-Aspalso inhibited histamine-induced elevation of cAMP. L-Asp itself did not affect the cAMP level although it ele-vated the cGMP level in the stomach.Moreover, either(+)2-amino-5-phosphonovaleric acid or(±)3-(2-carboxy-piperazin-4-yl)prophyl-1-phosphonic acid, i.e. two spe-cific antagonists for N-methyl-D-aspartic acid(NMDA)receptors, blocked the inhibitory effect of L-Asp on hista-mine-stimulated acid secretion or histamine-induced el-evation of cAMP. Since cAMP has been strongly impli-cated as the second messenger involved in histamine-induced acid secretion, we believe that L-Asp regulatesacid secretion in the stomach by inhibiting histaminerelease through the NMDA receptors, subsequently low-ering the level of cAMP and ultimately reducing acidsecretion.
- 中文關鍵字: --
- 英文關鍵字: Excitatory amino acids. NMDA receptor. L-Aspartic acid. cAMP. cGMP. Histamine. Acid Secretion