Regulation of atrial natriuretic peptide gene expression in gastric antrumby fasting

Atrial natriuretic peptide (ANP) gene expression was localized in the rat g astric antrum using immunohistochemistry and in situ hybridization to mucos al cells in the lower portion of the antropyloric glands. Colocalization of immunoreactive ANP, long-acting natriuretic peptide, i.e., proANP-(1-30), and serotonin in these cells identified them to be enterochromaffin cells. Fasting for 72 h in 8-mo-old (adult) rats produced a significant (P < 0.05) decrease in the levels of ANP prohormone mRNA, immunoreactive proANP-(1-90 ) and ANP to similar to 33% of that of fed rats. Fasting in 1-mo-old rats h ad no effect on these parameters. Transcripts for natriuretic peptide recep tor subtypes NPR-A, NPR-B, and NPR-C were found in both mucosa and muscle t issues of the antrum. ANP, brain natriuretic peptide (BNP), and C-type natr iuretic peptide (CNP) stimulated the production of cGMP in antral mucosa in vitro with a potency of ANP > BNP >> CNP, suggesting that these receptors were Functional. We conclude that fasting decreases ANP prohormone mRNA and its gene products, long-acting natriuretic peptide, and ANP in the antrum of adult rats.