A comparison of the effects of soluble stimuli on free cytoplasmic and membrane bound calcium in human neutrophils.
Calcium dynamics in human neutrophils have been studied using Quin 2 fluorescence as a measure of free cytoplasmic calcium and chlortetracycline fluorescence as an indicator of membrane-bound calcium. The results show that 1) FMLP-induced increased cytoplasmic calcium likely comes from at least two different pools. Calcium is released from one only after a high affinity receptor interaction and from the second also after a lower affinity interaction. The initial increment in cytosolic calcium does not appear to originate in the pool(s) reflected by CTC fluorescence. 2) Cytochalasin B strikingly alters the FMLP effect on membrane associated calcium, inducing a marked "recovery" phase which could be a reflection of fusion of granule membranes with the plasma membrane. 3) PMA, at concentrations inducing extensive specific granule release (less than or equal to 10 ng/ml) has no measurable direct effect on membrane-bound or cytosolic calcium. However, PMA inhibits a subsequent CTC fluorescence response to FMLP and following the ionophore, A23187, it induces a clear decrease in cytosolic calcium. These indirect effects may be explained in terms of PMA's activation of protein kinase C.
D000328:Adult; D000634:Aminoquinolines; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000097:blood*; D003571:Cytochalasin B / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D005456:Fluorescent Dyes; D006801:Humans; D007700:Kinetics; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000634:Aminoquinolines; D005456:Fluorescent Dyes; D000001:Calcimycin; D003571:Cytochalasin B; D009240:N-Formylmethionine Leucyl-Phenylalanine; D013755:Tetradecanoylphorbol Acetate; C035739:Quin2; D002118:Calcium