Immunohistochemical localization of angiotensin II receptor and local renin-angiotensin system in human colonic mucosa.

Angiotensin II (Ang II) regulates water and sodium transport in renal tubules and gastrointestinal tract. Two types of Ang II receptors have been cloned, but their distributions have not been determined in human colon. In addition, tissue renin-angiotensin systems (RAS) are believed to exist and to regulate local actions in human colon. We studied by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC) the presence and localization of Ang II receptors Type 1 (AT(1)), Type 2 (AT(2)), and RAS components [angiotensinogen, renin, and angiotensin-converting enzyme (ACE)] in normal human colon. AT(1) receptors were localized in vessel walls, myofibroblasts, macrophages, and surface epithelium. AT(2) receptors were found in mesenchymal cells and weakly in parts of surface epithelium. Renin and ACE were distributed in vessel walls, mesenchymal cells, and in parts of surface epithelium. Angiotensinogen was also detected by RT-PCR. These findings demonstrated that Ang II receptors and RAS components were present in human colon, suggesting the possibility of its local regulation.