A variety of substances, chemically heterogenous, has been classified as calcium antagonists. They inhibit the contractile activity of vascular smooth and cardiac muscle. This has been attributed to a blockade of the so called slow channels of the cell membrane causing an inhibition of the transmembrane influx of calcium. In the experiments reported we have studied the effect of verapamil, nifedipine and felodipine (pINN) on the uptake of calcium-45 in the rat portal vein and papillary muscle.

The results show that the substances, at their IC50 values, did not decrease the cellular uptake of calcium-45, measured with the lanthanum method.

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