[Vasodilator actions of felodipine, a new Ca2+ entry blocker]

Felodipine [ethylmethyl 4-(2,3-dichlorophenyl)-1,4-dihydro-2,6-dimethyl-3,5- pyridinedicarboxylate], a new Ca2+ entry blocker, relaxed isolated canine arteries and veins precontracted with prostaglandin (PG) F2 alpha, in a concentration-dependent manner. Felodipine dilated cerebral arteries predominantly over the other arteries. Relaxations by felodipine, in low concentrations, were greater in mesenteric vein strips than in mesenteric artery strips isolated from the same dogs. The inhibitory effect of felodipine in high concentrations (10(-7)M or higher) were not reversed by repeated washing. In coronary arteries exposed to Ca2+-free media under anoxia, PGF2 alpha and Ca2+ produced persistent contractions. Reoxygenation from anoxia elicited an additional contraction. Felodipine did not affect PGF2 alpha-induced contraction in Ca2+-free media, but significantly reduced the contractions caused by Ca2+ and reoxygenation. These findings suggest that felodipine is a potent, long-acting Ca2+ entry blocker with characteristics such as a greater action on cerebral arteries and mesenteric veins than coronary and mesenteric arteries.