title: Inhibition of endothelium-dependent smooth muscle relaxation by calmodulin antagonists.
abstract: By using the calmodulin antagonists, calmidazolium and N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide (W-7), the hypothesis was investigated as to whether calmodulin is involved in the sequence of events leading to the endothelium-dependent vascular smooth muscle relaxation. Endothelium-dependent relaxations were studied on two different preparations, the rabbit aorta and the pulmonary artery of the guinea pig. Relaxations were produced in the precontracted rings (noradrenaline 3 X 10(-6) mol/l) in response to acetylcholine, 10(-8) to 10(-6) mol/l (aorta), histamine, 3 X 10(-8) to 1 X 10(-6) mol/l (pulmonary artery) or the calcium ionophore A 23187, 1 X 10(-8) to 3 X 10(-7) mol/l (aorta and pulmonary artery). In the presence of calmidazolium and W-7 the endothelium-dependent relaxation was inhibited in a dose dependent manner. This inhibition was seen in a concentration range that coincides with calmodulin inhibition. The half maximal concentrations of calmidazolium for the inhibition of the relaxation of the aorta induced by acetylcholine and A 23187 were 3 X 10(-6) mol/l and 1.4 X 10(-6) mol/l and that of W-7 were 3.1 X 10(-5) and 3.6 X 10(-5) mol/l, respectively. Complete inhibition was obtained both for acetylcholine-and for A 23187-induced relaxations by preincubation with 1 X 10(-5) mol/l calmidazolium or 1 X 10(-4) mol/l W-7. The half maximal concentrations of calmidazolium for the inhibition of the relaxation of the pulmonary artery in response to histamine and A 23187 were 2.7 X 10(-6) mol/l and 3 X 10(-6) mol/l and complete inhibition was achieved at 1 X 10(-5) mol/l.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000502:physiology*; D004727:Endothelium / Q000502:physiology; D005260:Female; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009599:Nitroprusside / Q000494:pharmacology; D009638:Norepinephrine / Q000037:antagonists & inhibitors; D011817:Rabbits; D013449:Sulfonamides / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D002147:Calmodulin; D007093:Imidazoles; D013449:Sulfonamides; D009599:Nitroprusside; D000001:Calcimycin; C031938:calmidazolium; C017967:W 7; D006632:Histamine; D000109:Acetylcholine; D009638:Norepinephrine