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Characterization of endothelin-A receptors in the cerebral circulation
1Department of Experimental Research, Malmö General Hospital, Sweden.
Abstract:
Endothelin-1 (ET-1), a 21-amino acid peptide produced by the vascular endothelium, mediates contraction. In the present study we demonstrate that both ET-1 (Emax: 238 +/- 29% of potassium contraction) and ET-2 (Emax: 231 +/- 36%) produce strong concentration-dependent contractions of circular segments of guinea-pig middle cerebral artery, whereas ET-3 has only weak effects (Emax: 32 +/- 13%). FR 139317 (10(-6) M), a selective endothelinA (ETA) receptor antagonist, shifted the ET-1 response curve to the right (pD2:7.86 +/- 0.09 with and 8.76 +/- 0.09 without the antagonist) in a competitive manner (pA2 = 6.83). These findings are the first to show the presence of ETA receptors in cerebral vessels.