Structure-activity relationship of adrenomedullin, a novel vasodilatory peptide, in cultured rat vascular smooth muscle cells

Endocrinology. 1994 Dec;135(6):2454-8. doi: 10.1210/endo.135.6.7988431.


Vascular smooth muscle cells (VSMC) from rat aorta possess specific receptors for a novel potent vasorelaxant peptide, adrenomedullin (AM). To elucidate its receptor coupling to guanine nucleotide-binding stimulatory protein and the structural requirement of the AM molecule to its vascular receptors, we have studied the effects of guanine nucleotides on [125I]human (h) AM binding and adenylate cyclase activity in cultured rat VSMC, and the effects of various synthetic hAM analogs on [125I]hAM binding and the cAMP response. Guanosine 5'-O-(3-thiotriphosphate) dose dependently inhibited [125I]hAM binding to rat VSMC membranes. hAM stimulated adenylate cyclase activity, and its effect was additive with GTP. hAM-induced cAMP formation was abrogated by pretreatment with cholera toxin, but not by that with pertussis toxin. Intact hAM-(1-52)-NH2 and N-terminal truncated derivatives [hAM-(13-52)-NH2, hAM-(16-52)-NH2] almost equally inhibited [125I]hAM binding and stimulated cAMP formation, whereas removal of C-terminal Tyr52 residue [hAM-(1-51)-NH2] remarkably decreased receptor-binding activity and the cAMP response. The effects of hAM-(1-52)-OH, hAM-(1-51)-OH, and a linear hAM analog ([carbamoylmethyl-Cys16,21]hAM-NH2) were far less potent on receptor binding and the cAMP response than that of hAM-(1-52)-NH2. The C-terminal fragment [hAM-(33-52)-NH2] and the N-terminal fragment [hAM-(1-10)-OH] had neither receptor-binding nor adenylate cyclase activity. hAM-(22-52)-NH2 had no agonistic effect, but showed an antagonistic effect on the hAM-induced cAMP response. These data suggest that vascular AM receptors are functionally coupled to adenylate cyclase via guanine nucleotide-binding stimulatory protein. Studies of the structure-activity relationship of hAM revealed that the cyclic structure formed by the disulfide bridge and amidation of the C-terminal residue of the AM molecule are critical for receptor binding and subsequent cAMP generation and suggest that the C-terminal fragment hAM-(22-52)-NH2 may be an antagonist for vascular AM receptors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenylate Cyclase Toxin
  • Adenylyl Cyclases / metabolism
  • Adrenomedullin
  • Animals
  • Cell Membrane / metabolism
  • Cells, Cultured
  • Cholera Toxin / pharmacology
  • Cyclic AMP / biosynthesis
  • Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
  • Humans
  • Male
  • Muscle, Smooth, Vascular / cytology
  • Muscle, Smooth, Vascular / drug effects*
  • Peptides / chemistry*
  • Peptides / metabolism
  • Peptides / pharmacology*
  • Pertussis Toxin
  • Rats
  • Rats, Wistar
  • Structure-Activity Relationship
  • Vasodilator Agents / pharmacology*
  • Virulence Factors, Bordetella / pharmacology


  • Adenylate Cyclase Toxin
  • Peptides
  • Vasodilator Agents
  • Virulence Factors, Bordetella
  • Adrenomedullin
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • Cholera Toxin
  • Cyclic AMP
  • Pertussis Toxin
  • Adenylyl Cyclases