Atrial Natriuretic Peptide Gene Expression in the Rat Gastrointestinal Tract

The presence of ANP prohormone immunoreactivity in rat GI tract suggests that it may be an extracardiac site of ANP synthesis. The aim of this study was to investigate the expression of ANP mRNA in the adult rat GI tract. ANP mRNA was detected by ribonuclease protection analysis in stomach, small and large intestines, and rectum/anus. The highest concentrations of ANP transcripts were found in the proximal stomach, antrum, proximal colon, and rectum/anus at levels that ranged from 1 to 10% of that found in cardiac ventricle. Northern blot analysis of total RNA from these tissues identified a single 0.9 kb ANP transcript similar to that detected in heart. Gel filtration chromatography of tissue extracts provided evidence for the presence of the complete ANP prohormone in proximal stomach, antrum, proximal colon and rectum/anus. These results demonstrate that the gene for ANP is expressed in specific regions of the rat GI tract, suggesting that tissue-specific differential regulation of ANP synthesis occurs within the GI tract.