title: A spin-label study of plasma membranes of adrenal chromaffin cells.
abstract: Chromaffin-cell membranes were labeled with two nitroxide spin labels, one probing the interior of the membrane and one probing the interfacial region. Both spin labels indicate that the membrane undergoes a phase transition at about 26 degrees C. An Arrhenius plot of acetylcholinesterase activity exhibits a discontinuity at 26 degrees C, consistent with the existence of a phase transition at that temperature. Acetylcholine, which stimulates chromaffin cells to secrete catecholamines, and hexamethonium, a cholinergic blocker, do not affect the rotational correlation times of the spin labels. These results argue that cholinergic stimulation does not affect the fluidity of the chromaffin-cell membrane.
mesh_terms: D000110:Acetylcholinesterase / Q000032:analysis; D000313:Adrenal Medulla / Q000201:enzymology / Q000648:ultrastructure*; D000818:Animals; D002417:Cattle; D002458:Cell Fractionation; D002462:Cell Membrane / Q000201:enzymology / Q000648:ultrastructure*; D002838:Chromaffin System / Q000201:enzymology / Q000648:ultrastructure*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D008560:Membrane Fluidity; D013113:Spin Labels; D013816:Thermodynamics
chemical_list: D013113:Spin Labels; D000110:Acetylcholinesterase