Mechanisms of relaxing effect of hydrogen peroxide on bovine coronary artery

İn this in vitro study, the effects of H2 O2 on bovine coronary artery and roles of K+ channels and cyclooxygenase, nitric oxide synthase and Na+/K+-ATPase enzymes for these effects were investigated. Strips from arteries were mounted in 25 mİ organ baths containing Krebs-Henseleit Solution at 37 °C aerated with %95 O2 and %5 CO2 . Effects of H2 O2 on basal tone of tissues with and without endothelium were investigated. İn the second part of study, tissues were contracted with U46619 (3x10~7 M) and H2 O2 (1Cr7-1(T2M) was added to the organ baths, cumulatively. This procedure was repeated on tissues incubated with apamin (10~6M), charybdotoxin (10-7M), tetraethylammonium (TEA, 1Ch4M), glibenclamide (10-6M), indomethacin (10~5M), NG-nitro-L-arginine methyl ester (L-NAME, 10~4M) and ouabaine (10~5 M). Each group of tissue was incubated with only one of these agents. H2 O2 did not affect basal tone of tissues with and without endothelium but relaxed tissues contracted with U46619in con- centration dependent manner. İn tissues with endothelium and in tissues incubated with apamine, charybdotoxine and tetraethylammonium, Emax values and plC50 values of H2 O2 were not different significantly from values obtained from tissues vvithout endothelium (control tissues). However values obtained from tissues incubated with glibenclamide, indomethacin, L-NAME and ouabaine were different significantly from values obtained from tissues without endothelium.These results indicate that ATP-sensitive potassium channels and cyclooxygenase, nitric oxide synthase and Na+/K+-ATPase enzymes play role in the relaxant effects of H2 O2 on bovine coronary artery smooth muscle.