Modulation of calcium ion influx by the 1,4-dihydropyridines nifedipine and BAY K 8644.

We examined the effects of the new dihydropyridine calcium agonist BAY K 8644 on calcium influx and mechanical activity in rabbit aortic rings and compared them with those of the classical calcium antagonist nifedipine. The vasodilating effects of nifedipine and the vasoconstricting effects of BAY K 8644 can be explained by the calcium influx modulating activity of these two dihydropyridines. Only at the high concentration of 3 X 10(-6) mol/L BAY K 8644 is there a marked difference between increased calcium influx and reduced contraction.