Truncated atrial natriuretic peptide (ANP) analogs: relationship between receptor binding and cyclic GMP accumulation

The authors have shown that cultured bovine aortic smooth muscle (BASM) cells contain high affinity receptor sites for the ANP, auriculin (ANP(4-28)). Furthermore, ANP(4-28) causes cyclic GMP (cGMP) levels to increase in BASM. In the present study, the authors synthesized a series of NH/sub 2/ and/or COOH truncated ANP(4-28) analogs and examined their ability to compete for /sup 125/I-ANP(4-28) binding to BASM and increase cGMP levels. ANP-mediated cGMP responses were reduced when amino acids were deleted from the NH/sub 2/ and/or COOH termini of ANP(4-28). Removal of the NH/sub 2/ terminal R, R-S, or R-S-S residues resulted in a 10X decrease in potency for cGMP stimulation. Deletion of the COOH terminal R-Y and F-R-Y residues resulted in a marked decline in potency. ANP's lacking the F-R-Y tripeptide were nearly inactive in stimulating cGMP accumulation. In contrast to the cGMP effects, NH/sub 2/ and/or COOH truncations of ANP(4-28) did not alter apparent receptor binding affinities (Ki(app)). All of these peptide analogs exhibited Ki(app)'s of 1-5 nM. Furthermore, peptides that bound effectively and failed to elicit cGMP responses did not antagonize ANP(4-28)-mediated cGMP increases. These binding and functional data suggest the presence of a single class of ANP receptors on BASM ismore » insufficient to explain the actions of ANP's in these cells.« less