Apparent noncompetitive antagonism of muscarinic receptor mediated Ca2+ mobilization by some muscarinic antagonists.
Ca2+ mobilizations in SH-SY5Y and IMR-32 human neuroblastoma cell lines were measured using the fluorescent Ca2+ indicator fura-2. A variety of antagonists (atropine, pirenzepine, 4-DAMP and N-methyl-scopolamine) inhibited carbamyl choline-induced transient Ca2+ mobilization both in a competitive and a noncompetitive manner. The apparent noncompetitive inhibition constants were lower in IMR-32 than in SH-SY5Y cells even when the competitive inhibition constants were similar. This may relate to the previously reported differential expression of muscarinic receptor subtypes in these cell lines.
Kukkonen
J
J
Department of Biochemistry and Pharmacy, Abo Akademi University, Turku, Finland.
Akerman
K E
KE
D001285:Atropine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D016257:Fura-2; D006801:Humans; D007700:Kinetics; D018727:Muscarinic Antagonists; D019832:N-Methylscopolamine; D009447:Neuroblastoma; D010276:Parasympatholytics / Q000494:pharmacology*; D010880:Piperidines / Q000494:pharmacology*; D010890:Pirenzepine / Q000494:pharmacology*; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology*; D012602:Scopolamine Derivatives / Q000378:metabolism / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence; D014407:Tumor Cells, Cultured
D018727:Muscarinic Antagonists; D010276:Parasympatholytics; D010880:Piperidines; D011976:Receptors, Muscarinic; D012602:Scopolamine Derivatives; D010890:Pirenzepine; D001285:Atropine; C042375:4-diphenylacetoxy-1,1-dimethylpiperidinium; D002118:Calcium; D016257:Fura-2; D019832:N-Methylscopolamine