Angiotensin II type 2 receptor-mediated duodenal mucosal alkaline secretion in the rat

The aims of this study were to elucidate the distribution of angiotensin re ceptors (AT(1) and AT(2)) in the duodenal wall and to investigate whether A T(2) receptors are involved in the regulation of duodenal mucosal alkaline secretion, which is of importance for the mucosal defense against gastric a cid. Immunohistochemistry was used to locate AT(1) and AT(2) receptors in c hloralose-anesthetized rats. Duodenal mucosal alkaline output was measured by use of in situ pH-stat titration. Immunohistochemistry demonstrated a di stinct staining for both AT(1) and AT(2) receptors in the lamina propria of the villi and also for AT(1) receptors in the muscularis interna. When ang iotensin II was infused in the presence of the AT(1) receptor antagonist lo sartan, mucosal alkaline secretion increased by similar to 50%. This respon se was inhibited by the AT(2) receptor antagonist PD-123319. The AT(2) rece ptor agonist CGP-42112A increased mucosal alkaline secretion by similar to 50%. This increase was absent in the presence of PD-123319 but not in the p resence of losartan or the local anesthetic lidocaine. We conclude that ang iotensin II stimulates duodenal mucosal alkaline secretion by activation of AT(2) receptors located in the duodenal mucosa/submucosa.