title: Differential labelling of putative skeletal muscle calcium channels by [3H]-nifedipine, [3H]-nitrendipine, [3H]-nimodipine and [3H]-PN 200 110.
abstract: Four 1,4-dihydropyridine calcium channel blockers [3H]-nifedipine, [3H]-nitrendipine, [3H]-nimodipine and [3H]-PN 200 110 (Isopropyl 4-(2,1,3,benzoxadiazol-4-yl)-1,4-dihydro-2,6-dimethyl-5-methoxy- carbonylpyridine-3-carboxylate) were employed to label putative calcium channels in guinea-pig hind limb skeletal muscle membranes. The four radioligands differed with respect to the number of sites (Bmax) which were labelled. The following rank order of Bmax values was found: PN 200 110 greater than nimodipine = nitrendipine greater than nifedipine. d-cis-Diltiazem caused an increase in the density of high-affinity binding sites for all four calcium channel blockers. The relative stimulation was smallest for PN 200 110. It is suggested that 1,4-dihydropyridines exhibit different efficacies for induction of a channel state with high affinity for these drugs.
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007473:Ion Channels / Q000378:metabolism*; D017275:Isradipine; D007700:Kinetics; D009132:Muscles / Q000378:metabolism*; D009539:Nicotinic Acids / Q000378:metabolism; D009543:Nifedipine / Q000031:analogs & derivatives / Q000378:metabolism; D009553:Nimodipine; D009568:Nitrendipine; D010069:Oxadiazoles / Q000378:metabolism
chemical_list: D002121:Calcium Channel Blockers; D007473:Ion Channels; D009539:Nicotinic Acids; D010069:Oxadiazoles; D009553:Nimodipine; D009568:Nitrendipine; D009543:Nifedipine; D017275:Isradipine