The calcium channel antagonist S 11568 causes endothelium-dependent relaxation in canine arteries

The new dihydropyridine calcium channel antagonist S 11568 and its optical isomers, S 12967 and S 12968 (3 × 10 −6 to 10 −4 M), caused, unlike nifedipine (10 −4 M), equipotent and rapid endothelium-dependent relaxations and increased the content of cyclic GMP in rings of canine femoral arteries. These effects were observed in the presence of indomethacin and were prevented by methylene blue, hemoglobin and N G-monomethyl-L-arginine. Thus these effects must involve endothelium-derived relaxing factor (EDRF) and be distinct from the calcium channel antagonistic effect which is stereoselective and of slow onset. The compounds did not potentiate relaxations of rings without endothelium to nitric oxide. In bioassay experiments, the compounds produced endothelium-dependent relaxation only when applied to endothelial donors. These results are compatible with an increased release of EDRF induced by the dihydropyridine compounds.