title: Putative calcium channel molecular weight determination by target size analysis.
abstract: The molecular weight of the putative calcium channel in guinea-pig brain membranes, labelled with [3H]-nimodipine, has been determined in situ by target size analysis. Irradiation of guinea-pig brain membranes at 153-173 K with 10 MeV electrons reduced the density of [3H]-nimodipine binding sites without affecting the equilibrium dissociation constant. The decay of the calcium channel blocker binding site density as a function of radiation dose fits to a monoexponential function. Application of the target size theory gives a molecular weight of 185,000. [3H]-Flunitrazepam labelled benzodiazepine receptor target size was measured as an internal control. The molecular weight of the benzodiazepine receptors was 76,000, which is in good agreement with published results.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D005260:Female; D005445:Flunitrazepam; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007473:Ion Channels / Q000032:analysis*; D007700:Kinetics; D008297:Male; D008566:Membranes / Q000378:metabolism; D008970:Molecular Weight; D009539:Nicotinic Acids; D009553:Nimodipine; D011869:Radioligand Assay; D011956:Receptors, Cell Surface / Q000378:metabolism; D011963:Receptors, GABA-A
chemical_list: D007473:Ion Channels; D009539:Nicotinic Acids; D011956:Receptors, Cell Surface; D011963:Receptors, GABA-A; D009553:Nimodipine; D005445:Flunitrazepam; D002118:Calcium