title: The role of calcium and cyclic adenosine 3',5'-monophosphate in the regulation of glycogen metabolism in phagocytozing human polymorphonuclear leukocytes.
abstract: Incubation of human polymorphonuclear leukocytes in a glucose-free Krebs-Ringer bicarbonate buffer for 2 h resulted in glycogen depletion, decreased phosphorylase activity and increased synthase-R activity. Addition of dialyzed latex particles to starved leukocytes revealed a very rapid ingestion rate (half-maximal ingestion within 30 s). This uptake is followed by glycogenolysis associated with an immediate two-fold increase in phosphorylase a activity and a synthase-R to -D conversion within 30 s. Furthermore, in rapid time-course experiments with phagocytozing cells we found that the concentration of cyclic AMP increased by 93% within 15 s and returned to baseline values at 1 min. In a medium without added calcium and with 1 mM ethyleneglycol-bis-(beta-aminoethylether)-N,N'-tetraacetic acid, phagocytosis was blocked, cyclic AMP formation decreased by 50% and phosphorylase activation was abolished, but the conversion of synthase-R to -D was preserved. Addition of calcium ions to cells suspended in a calcium-free buffer without added latex results in phosphorylase activation and glycogenolysis, but not in cyclic AMP increase or synthase-R to -D conversion. Measurements of 45Ca efflux during phagocytosis suggest an initial increase in cytosolic calcium obtained by a release of membrane-bound 45Ca. Activation of phosphorylase during phagocytosis is thus presumably due to an increase in cytosol Ca2+ and subsequent activation of phosphorylase kinase, and is independent of the simultaneous increase in concentration of cyclic AMP. Phosphorylation of synthase R to the D form does not depend on the presence of Ca2+ in the extracellular phase.
mesh_terms: D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D006003:Glycogen / Q000378:metabolism*; D006006:Glycogen Synthase / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007840:Latex; D008274:Magnesium / Q000494:pharmacology; D008863:Microspheres; D009504:Neutrophils / Q000378:metabolism*; D010587:Phagocytosis / Q000187:drug effects; D006005:Phosphorylases / Q000378:metabolism; D013217:Starvation; D013997:Time Factors
chemical_list: D007840:Latex; D004533:Egtazic Acid; D006003:Glycogen; D000242:Cyclic AMP; D006005:Phosphorylases; D006006:Glycogen Synthase; D008274:Magnesium; D002118:Calcium