Endothelin and Ca++ agonist Bay K 8644: different vasoconstrictive properties.
The mechanism of vasoconstriction induced by endothelin was investigated in rat isolated aorta in comparison with the Ca++ agonist, Bay K 8644. Endothelin (EC50 = 4 nM) induced a slow and sustained contraction in control medium whereas the one elicited by Bay K 8644 (EC50 = 14 nM) necessitating a partly K+ depolarized medium was fast with superimposed rhythmic contraction. By opposition with Bay K 8644, endothelin contraction was not inhibited by the calcium antagonists (1 microM), nifedipine, diltiazem and D 600, and substantially persisted in Ca++ free medium or after depletion of intracellular Ca++ by phenylephrine (1 microM). These data show that endothelin does not act as an activator of potential dependent Ca++ channels but probably through specific receptor(s) as suggested by its mode of vasoconstriction.
Auguet
M
M
Institut Henri Beaufour, Les Ulis, France.
Delaflotte
S
S
Chabrier
P E
PE
Pirotzky
E
E
Clostre
F
F
Braquet
P
P
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D004110:Diltiazem / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D016232:Endothelins; D005711:Gallopamil / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology*; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D014662:Vasoconstrictor Agents
D016232:Endothelins; D010455:Peptides; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D010656:Phenylephrine; D005711:Gallopamil; D004533:Egtazic Acid; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002217:Carbachol; D004110:Diltiazem; D009543:Nifedipine; D002118:Calcium