Author(s): Poli E, Casoli C, Spaggiari I, Starcich R, Bertaccini G
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Abstract The contractile effect of endothelin-2 was investigated in isolated human saphenous vein preparations. Spare segments taken from revascularized patients were set up in isolated organ chambers and mechanical activity was recorded under isometric conditions. Endothelin-2 (10(-11)-10(-7) M) evoked a dose-dependent contractile response, having the same efficacy as noradrenaline and 100 times its potency. Conversely, the "selective" ETB agonist, C-terminal hexapeptide endothelin (16-21), was completely ineffective. The activity of endothelin-2 was not modified by phentolamine, saralasin and indomethacin, thus excluding a direct or indirect activation of alpha-adrenoceptors and angiotensin receptors as well as the synthesis of cyclooxygenase products. Calcium removal from nutrient fluid depressed, but not fully abolished, the contractile effect of endothelin-2; furthermore, calcium channel blockers, verapamil and nifedipine, produced only a partial inhibition of the endothelin-2-induced contractions. These observations suggest that endothelin-2 induces a direct activation of specific receptors in the saphenous vein muscle and that both intracellular and extracellular calcium pools may be involved in the contractile effect of the peptide.
This article was published in Arch Int Pharmacodyn Ther
and referenced in Journal of Hypertension: Open Access