The interaction of [³H]nitrendipine with receptors for calcium antagonists in the cerebral cortex and heart of rats

The binding properties of the calcium antagonist, [³H]nitrendipine, were investigated in homogenates of the rat cerebral cortex and myocardium. The specific component of [³H]nitrendipine binding was consistent with mass action behavior and was described by a high affinity dissociation constant in the range of 0.1 - 0.3 nM. [³H]nitrendipine binding was sensitive to inhibition by other calcium antagonists and by the cations Ca⁺² and La⁺³. The inhibition of [³H]nitrendipine binding by verapamil was not of the simple competitive type but resembled allosteric inhibition, suggesting that there are at least two binding sites for calcium antagonists.