Chickens Express Only Uroguanylin for Regulation of cGMP Production

Genes encoding uroguanylin and guanylin are found in all vertebrates that have been investigated thus far. Both peptides activate a receptor‐guanylate cyclase‐C (R‐GC‐C) signaling molecule. In this study, cDNAs were isolated encoding chicken forms of preprouroguanylin and R‐GC‐C. A bioactive uroguanylin peptide is located at the C‐terminus of a 110 residue precursor. Chicken uroguanylin stimulates cGMP production in human T84 intestinal and opossum kidney cells. Uroguanylin genes are located on chromosome 21 and genes encoding R‐GC‐C on chromosome 1 of Gallus gallus . Uroguanylin alone regulates the enzymatic activity of R‐GC‐C in chickens because no evidence for genes encoding preproguanylin was found in the database from the Chicken Genone project. Transcripts for uroguanylin were detected in the small and large intestine, liver, pancreas, fat, uterus, magnum and heart. R‐GC‐C mRNAs were detected in the intestine, pancreas, fat, magnum and kidney. Administration of oral NaCl increases mRNA levels for uroguanylin and R‐GC‐C in the intestine, kidney and magnum segment of oviduct. Therefore, chickens express uroguanylin alone and no guanylin for regulation of R‐GC‐C enzyme activity and cGMP production in target organs. Dietary salt influences both uroguanylin and R‐GC‐C mRNAs in tissues involved in sodium balance like the intestine and kidney as well as novel tissues such as the magnum segment of avian oviduct.