Modulation of alpha-adrenergic-induced contractions by endothelium-derived relaxing factor in rat aorta.
1. In rat thoracic aorta, endothelium removal produced a significant increase of the maximal contraction (Emax) and of the pD2 value (-log ED50) induced by norepinephrine, phenylephrine and clonidine, and did not affect the maximal contractile response to 70 mM KCl. 2. Clonidine did not induce a contraction in aorta with intact endothelium, but after endothelium removal, the contractile response was 94.8% of the Emax produced by norepinephrine in aorta with endothelium. 3. Pre-incubation with methylene blue (10(-5) M) and hemoglobin (0.02%), which inhibit EDRF effects, produced the same effects as the mechanical removal of endothelium on the contractile responses to alpha-adrenergic agonists. 4. These results suggest that EDRF formation and release is an important factor in the modulation of alpha-adrenergic-induced vasoconstriction.
Department of Pharmacology, Faculty of Medicine, University of Chile, Santiago.
R
R
Vinet
C
C
Brieva
G
G
Pinardi
M
M
Penna
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D003000:Clonidine / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology*; D066298:In Vitro Techniques; D008751:Methylene Blue / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009569:Nitric Oxide / Q000494:pharmacology*; D009609:Nitrous Oxide / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*
D000316:Adrenergic alpha-Agonists; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D009569:Nitric Oxide; D011189:Potassium Chloride; D009609:Nitrous Oxide; D003000:Clonidine; D008751:Methylene Blue; D009638:Norepinephrine