Adrenomedullin stimulates two signal transduction pathways, cAMP accumulation and Ca2+ mobilization, in bovine aortic endothelial cells.
The biological action of adrenomedullin, a novel hypotensive peptide, on bovine aortic endothelial cells, was examined. The specific binding of adrenomedullin to these cells was observed, and adrenomedullin was found to induce intracellular cAMP accumulation in a dose-dependent manner. EC50 for the cAMP accumulation was about 100 times lower than the apparent IC50 for the binding assay. Adrenomedullin also induced increase of intracellular free Ca2+ in endothelial cells in a dose-dependent manner. The Ca2+ response to adrenomedullin was biphasic with an initial transient increase due to the release from thapsigargin-sensitive intracellular Ca2+ storage and a prolonged increase by influx through the ion channel on the plasma membrane. This intracellular free Ca2+ increase resulted from phospholipase C activation and inositol 1,4,5-trisphosphate formation, and seemed to cause nitric oxide synthase activation by monitoring intracellular cGMP accumulation. Both cAMP accumulation and Ca2+ increased responses to adrenomedullin were mediated by cholera toxin-sensitive G protein, but the two signal transduction pathways were independent. Thus, the results suggest that adrenomedullin elicits the hypotensive effect through at least two mechanisms, a direct action on vascular smooth muscle cells to increase intracellular cAMP and an action on endothelial cells to stimulate nitric oxide release, with both leading to vascular relaxation.
Shimekake
Y
Y
Shionogi Research Laboratories, Shionogi & Company, Ltd., Osaka, Japan.
Nagata
K
K
Ohta
S
S
Kambayashi
Y
Y
Teraoka
H
H
Kitamura
K
K
Eto
T
T
Kangawa
K
K
Matsuo
H
H
D053607:Adrenomedullin; D000818:Animals; D001011:Aorta / Q000166:cytology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D010455:Peptides / Q000502:physiology*; D015398:Signal Transduction
D010455:Peptides; D053607:Adrenomedullin; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D006152:Cyclic GMP; D002118:Calcium