Effects of oxodipine and elgodipine on (+)‐[3H]‐isradipine binding to cardiac and vascular membranes: cardiovascular selectivity

We studied the effects of six dihydropyridines on the specific binding of (+)-[3H]-isradipine to vascular (portal vein) and cardiac isolated membranes to achieve the relative cardiovascular selectivity of these compounds. Elgodipine, (+)-oxodipine and nifedipine had a significantly higher affinity for the vascular L-type calcium channel than for the cardiac calcium channel while nicardipine showed opposite properties. The other dihydropyridines (nitrendipine and (+)-isradipine) had similar affinities for the cardiac and vascular calcium channels. As the membrane potential of isolated membranes is about 0 mV, these results suggest that the differences in binding of these dihydropyridines to L-type calcium channels in vascular and cardiac cells may be attributed to differences in the molecular structure of these calcium channels.