title: [3H]nitrendipine binding in the guinea pig left ventricle: effects of calcium and lanthanum.
abstract: The purpose of this study was to investigate the effects of Ca2+ and La3+ on [3H]nitrendipine binding in the heart. [3H]Nitrendipine binding in EDTA washed (10 mM) membrane preparations of the guinea pig left ventricle showed a single class of specific high affinity binding sites with a dissociation constant (Kd) of 90 +/- 3.4 pM (mean +/- S.E.M.; n = 5) and a maximal number of binding sites (Bmax) of 70.5 +/- 6.3 fmol/mg protein. Ca2+ (2 mM) increased the Bmax to about 154% of control. EDTA and La3+ both reduced the number of binding sites, and their effects were antagonized by Ca2+. Ca2+ (10 mM) also shifted the La3+ concentration-dependent inhibition of [3H]nitrendipine binding to the right (IC50 = 10.4 and 22.8 microM respectively). These results suggest that Ca2+ is required for [3H]nitrendipine binding in the guinea pig heart and that La3+ antagonizes the effect of Ca2+.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000378:metabolism*; D004492:Edetic Acid / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007811:Lanthanum / Q000494:pharmacology*; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009543:Nifedipine / Q000031:analogs & derivatives* / Q000378:metabolism; D009568:Nitrendipine; D014316:Tritium
chemical_list: D002121:Calcium Channel Blockers; D014316:Tritium; D007811:Lanthanum; D009568:Nitrendipine; D004492:Edetic Acid; D009543:Nifedipine; D002118:Calcium