A novel 1,4-dihydropyridine-binding site on mitochondrial membranes from guinea-pig heart, liver and kidney.
The 1,4-dihydropyridine (+/-)-[3H]nitrendipine reversibly binds to mitochondrial preparations from guinea-pig heart with a dissociation constant (Kd) of 593 +/- 77 nM and a maximum density of binding sites (Bmax.) of 1.75 +/- 0.27 nmol/mg of protein. This low-affinity high-capacity 1,4-dihydropyridine-binding site does not discriminate between the enantiomers of nitrendipine and is also found in mitochondrial membranes from guinea-pig liver (Kd 586 +/- 91 nM; Bmax. 0.36 +/- 0.04 nmol/mg of protein) and kidney (Kd 657 +/- 149 nM; Bmax. 0.56 +/- 0.12 nmol/mg of protein). Phenylalkylamines (e.g. verapamil) inhibit ( +/- )-[3H]nitrendipine binding with micromolar inhibition constants, but the benzothiazepine D-cis-diltiazem, a potent Ca2+-channel blocker, is without effect. The binding is heat-stable, shows a V-shaped pH-dependence with a minimum around pH 7.0, and is strongly dependent on ionic strength in the incubation medium. The cations La3+ greater than Cd2+ much greater than Co2+ greater than Ca2+ much greater than Ba2+ greater than Mg2+ greater than Li+ greater than Na+ and the anions NO3- greater than C1- greater than or equal to F- stimulate the binding, whereas PO4(3-) greater than SO4(2-) slightly inhibit it. The low-affinity ( +/- )-[3H]nitrendipine-binding site located on the mitochondrial inner membrane is biochemically and pharmacologically different from the 1,4-dihydropyridine-receptor domain of the L-type Ca2+ channel. Furthermore, it is not identical with any of the low-affinity 1,4-dihydropyridine-binding sites described so far.
Institut für Biochemische Pharmakologie, Universität Innsbruck, Austria.
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Zernig
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Glossmann
D000818:Animals; D001665:Binding Sites; D002499:Centrifugation, Density Gradient; D004095:Dihydropyridines / Q000378:metabolism*; D004110:Diltiazem / Q000494:pharmacology; D006168:Guinea Pigs; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D008929:Mitochondria, Heart / Q000378:metabolism; D008930:Mitochondria, Liver / Q000378:metabolism; D009568:Nitrendipine / Q000378:metabolism; D009994:Osmolar Concentration; D013347:Subcellular Fractions / Q000378:metabolism; D014700:Verapamil / Q000031:analogs & derivatives / Q000494:pharmacology
D004095:Dihydropyridines; C038806:1,4-dihydropyridine; D009568:Nitrendipine; D014700:Verapamil; D004110:Diltiazem