The endothelin system in normal human colon

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Abstract
Endothelin (ET)-1 is a potent vasoconstrictor and mitogenic peptide that has a variety of biological effects in noncardiovascular tissues. The precise cellular distribution of the ET-1 system in the wall of the normal human colon was studied to identify the physiological role of ET in the gut. In situ hybridization revealed ET-converting enzyme-1 (ECE-1) mRNA in all vessels, the colon epithelium, and macrophages. Prepro-ET-1 (PPET-1) mRNA had a similar distribution except for a scattered signal in mucosal microvessels. ETAand ETBreceptor mRNAs were mainly in the lamina propria, pericryptal myofibroblasts, microvessels, and mononuclear cells, with ETAmRNA more abundant than ETBmRNA.125I-ET-1 binding showed ETBalong the crypts and in nerve fibers descending from the ganglionic plexus that contained PPET-1, ECE-1, and ETBtranscripts, whereas glia contained ETAreceptors. The finding of the entire ET system in the normal mucosa suggests its implication in some characteristic functions of the colon and its secretion as both a neuroactive and a vasoactive peptide.