title: Analysis of the positive-inotropic activity of the benzimidazole derivative AR-L 115 BS in isolated guinea pig atria.
abstract: When comparing the positive-inotropic effect of 2-[(2-methoxy-4-methylsulfinyl)phenyl]-1H-imidazo[4,5-b]pyridine (AR-L 115 BS) on the isolated guinea pig atria with those of theophylline, orciprenaline and strophanthin G, the following results were obtained: 1. In left atria the maximum effective concentration of AR-L 115 BS is 3.16 x 10(-4), of theophylline 10(-3), of strophanthin G 6.81 x 10(-7) and of orciprenaline 10(-5) mol/l. The increase in the contractile force thereby obtained was 192, 111, 158 and 277%, respectively (extracellular calcium concentration 1.2 mmol/l). Therefore AR-L 115 BS is somewhat less effective than orciprenaline but more effective than theophylline and strophanthin G. 2. AR-L 115 BS is also effective in atria isolated from animals pretreated with reserpine and its effect is not reduced in the presence of bupranolol. 3. Contrary to strophanthin G, AR-L 115 BS has a shorter time of onset of activity and is less dependent on the extracellular calcium concentration. 4. Similar to theophylline, AR-L 115 BS inhibits the positive-inotropic effect of orciprenaline dose-dependently, while strophanthin G increases the positive-inotropic effect of orciprenaline. 5. The effect of AR-L 115 BS differs from that of orciprenaline in having only little effect on the contraction rate in isolated right atrial preparations.
mesh_terms: D000818:Animals; D002046:Bupranolol / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology*; D004347:Drug Interactions; D006168:Guinea Pigs; D007093:Imidazoles / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009921:Metaproterenol / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects*; D010042:Ouabain / Q000494:pharmacology; D012110:Reserpine / Q000494:pharmacology; D013268:Stimulation, Chemical; D013806:Theophylline / Q000494:pharmacology
chemical_list: D002316:Cardiotonic Agents; D007093:Imidazoles; D009921:Metaproterenol; D010042:Ouabain; D002046:Bupranolol; D012110:Reserpine; D013806:Theophylline; C029758:sulmazole