Modulation of Calcium Ion Influx by the 1,4-Dihydropyridines Nifedipine and BAY K 8644

Abstract
The effects of the new dihydropyridine Ca agonist BAY K 8644 [1,4-Dihydro-2,6-dimethyl-5-nitro-4-[2-(trifluoromethyl)phenyl]pyridinecarboxylic acid methyl ester] on Ca influx and mechanical activity was examined in rabbit aortic rings and compared with those of the classical Ca antagonist nifedipine. The vasodilating effects of nifedipine and the vasoconstricting effects of BAY K 8644 were explained by the Ca influx modulating activity of these 2 dihydropyridines. Only at the high concentration of 3 .times. 10-6 mol/l BAY K 8644 was there a marked difference between increased Ca influx and reduced contraction.