Imidazole-induced potentiation of the contractile response to various agonists in vascular smooth muscle.
In isolated rabbit aortae, imidazole (10(-4)M) caused a unique nonspecific potentiation of the contractile responses to prostaglandins, norepinephrine, 5-hydroxytryptamine, histamine and potassium only at low concentrations. Imidazole had no effect on the dose-response relationship for Ca2+ in the presence of potassium, 40 mM. Imidazole potentiated contractions in supersensitive strips pretreated with reserpine or with low temperature (5 degrees C) for 5 days. In the presence of theophylline (3 x 10(-4)M), imidazole failed to potentiate the responses to norepinephrine, 5-hydroxy-tryptamine, histamine and potassium, but significantly potentiated responses to prostaglandin E1, E2 and F2 alpha. Imidazole (10(-4)M) significantly decreased the 45Ca uptake of aorta in a Ca-free solution, whereas the drug did not affect 45Ca uptake in a normal solution. These results suggest that imidazole-induced potentiation is related to an increase in Ca2+ permeability and possibly to an additive effect on Ca2+ binding.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004357:Drug Synergism; D005260:Female; D007093:Imidazoles / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D011465:Prostaglandins, Synthetic / Q000494:pharmacology; D011817:Rabbits; D012110:Reserpine / Q000494:pharmacology; D013806:Theophylline / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
D007093:Imidazoles; D011465:Prostaglandins, Synthetic; D014662:Vasoconstrictor Agents; C029899:imidazole; D012110:Reserpine; D013806:Theophylline; D000242:Cyclic AMP; D002118:Calcium