title: 3,4,5-Triiodobenzoic acid affects [3H]verapamil binding to plant and animal membrane fractions and smooth muscle contraction.
abstract: 3,4,5-Triiodobenzoic acid, known as auxin transport inhibitor, stimulates specific [3H]verapamil binding to zucchini microsomes by 100% (EC50 = 1 microM). This stimulatory effect is due to a decrease of the apparent equilibrium dissociation constant KD for verapamil from 60 nM to 33 nM without significantly changing the maximum number of binding sites. 3,4,5-Triiodobenzoic acid also increases specific [3H]verapamil binding to rabbit skeletal muscle membranes (EC50 greater than or equal to 20 microM) without affecting [3H]nitrendipine and [3H]-d-cis-diltiazem binding. If 3,4,5-triiodobenzoic acid is added to isolated rings of rabbit A. saphena contracted by potassium depolarization, a dose-dependent relaxation is observed with an IC50 value of about 8 microM. Contractions initiated by the addition of 3 microM norepinephrine can also be abolished by 3,4,5-triiodobenzoic acid with half maximal inhibition at 40 microM.
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers; D002462:Cell Membrane / Q000378:metabolism; D066298:In Vitro Techniques; D007210:Indoleacetic Acids / Q000502:physiology*; D007463:Iodobenzoates / Q000494:pharmacology*; D008861:Microsomes / Q000378:metabolism; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009132:Muscles / Q000378:metabolism; D010937:Plant Growth Regulators / Q000502:physiology*; D010944:Plants; D011817:Rabbits; D014283:Triiodobenzoic Acids / Q000494:pharmacology*; D014700:Verapamil / Q000378:metabolism*
chemical_list: D002121:Calcium Channel Blockers; D007210:Indoleacetic Acids; D007463:Iodobenzoates; D010937:Plant Growth Regulators; D014283:Triiodobenzoic Acids; D014700:Verapamil; D002118:Calcium