Effects of AR-L 115 BS on arterial and venous muscle tone in vitro.

The effects of the cardiotonic drug 2-[(2-methoxy-4-methyl-sulfinyl)phenyl]-1H-imidazo[4,5-b]pyridine (AR-L 115 BS) on strips from isolated human veins and on strips from bovine veins and arteries were studied. The effects depended on the type and on the site of origin of the vessel. Pre-stretched human saphenous vein strips always relaxed in presence of AR-L 115 BS (greater than 10(-4) mol/l) while jugular vein strips seemed rather unaffected. Pre-stretched bovine facial vein strips always relaxed in presence of AR-L 115 BS, proximal branches being significantly more sensitive to the drug than distal branches. In bovine facial arteries AR-L 115 BS (greater than 10(-4) mol/l) produced either no change or a small increase in tension. When the arteries were pre-contracted by application of 50 mmol/l K+, low concentrations (less than 10(-5) mol/l) increased the tension while high concentrations (greater than 10(-5) mol/l) induced relaxation. The relaxing power of AR-L 115 BS on pre-contracted vein strips seemed better than that of nifedipine and less than that of Na nitroprusside.