Effects of Light and BAY K 8644, a New 1,4‐Dihydropyridine, on Mechanical Responses of Rat Thoracic Aorta

Publisher Website
Google Scholar
Abstract
The effect of day light and UV radiation (360 nm) on mechanical responses to BAY K 8644 (methyl-1,4-dihydro-2,6-dimethyl-3-nitro-4-(-2-trifluoromethylphenyl)-pyridine-5-carboxylate), K+ and noradrenaline [norepinephrine] (NA) or rat aorta rings was investigated. The contractile response to BAY K 8644 (10-6 M) obtained before and after exposure of the BAY K 8644 stock solution to UV radiation was unchanged and equal to that of K+ (125 mM). UV radiation and day light did not affect responses evoked by K+ (125 mM) and NA (1.8 .times. 10-5 M). In contrast to this both types of light relaxed vessels contracted by BAY K 8644 (10-6 M). The light induced relaxations were reversible, unaffected by addition of propranolol (3 .times. 10-6 M) and could not be eliminated by washing the preparations repeatedly with Krebs solution. In vessels contracted by K+ (125 mM) and NA (1.8 .times. 10-5 M) UV radiation induced a reversible relaxation in the presence of BAY K 8644. BAY K 8644 (10-4 M) and nifedipine (10-8 M) relaxed preparations contracted by K+. Nifedipine (10-6 M) totally relaxed preparations contracted by BAY K 8644 (10-6 M). UV radiation eliminated the relaxant effect of nifedipine and decreased the relaxant effect of nifedipine and decreased the relaxant effect of BAY K 8644 (10-4 M). BAY K 8644 apparently is more light-stable than nifedipine and BAY K 8644 sensitized the vascular smooth muscle to UV radiation as well as day light. Consequently this should be taken into account when BAY K 8644 is studied.