title: Dihydropyridine [methyl-3H]PN 200-110 binding and myogenesis in intact muscle cells in vitro.
abstract: The radioligand dihydropyridine [methyl-3H]PN 200-110 binds to contracting myotubes in culture derived from chick embryo pectoralis muscle. [methyl-3H]PN 200-110 binds specifically to high-affinity sites, with nonspecific binding only between 15 and 30% of the total binding. A Scatchard plot of the specific binding revealed a single high-affinity binding site with a KD (dissociation constant) of 0.5 nM +/- 0.2 nM and Bmax (number of binding sites) of 100 fmol/10(6) nuclei. We employed this sensitive assay to probe the appearance of high-affinity [methyl-3H]PN 200-110 binding sites during myogenesis. The time course of appearance of high-affinity binding sites lags behind that of fusion. Low-calcium media prevented the differentiation of myoblasts and blocked the appearance of high-affinity sites. Chelation of intracellular calcium before or after fusion of myoblasts with the calcium indicator Quin 2 prevented the appearance of dihydropyridine binding sites. These findings are consistent with the view that the expression of dihydropyridine receptors is modulated by the intracellular calcium.
mesh_terms: D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000502:physiology; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002478:Cells, Cultured; D002642:Chick Embryo; D017275:Isradipine; D007700:Kinetics; D009132:Muscles / Q000196:embryology* / Q000378:metabolism; D009543:Nifedipine / Q000031:analogs & derivatives / Q000378:metabolism; D009568:Nitrendipine; D010069:Oxadiazoles / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000634:Aminoquinolines; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D010069:Oxadiazoles; D011978:Receptors, Nicotinic; D009568:Nitrendipine; D009543:Nifedipine; C035739:Quin2; D002118:Calcium; D017275:Isradipine