| Abstract: | Exposure of HL-60 cells for 6 days to a combination of 1.25% (v/v) dimethyl sulfoxide and 10 microM dexamethasone induces myeloid differentiation which results in a cell with many of the characteristics of a mature granulocyte. At 4 degrees C myeloid differentiated, but not undifferentiated, monocytic differentiated or eosinophilic differentiated HL-60 cells display marked specific leukotriene B4 binding. Leukotriene B4 binding at 4 degrees C reaches a maximum within 10 min, is readily reversed by unlabeled leukotriene B4, and is stereospecific. Only molecules with structural and biological similarity to leukotriene B4 can competitively inhibit leukotriene B4 binding. Scatchard analysis at 4 degrees C in differentiated cells shows two classes of binding sites. The high affinity sites have a Kd of 0.27 nM and a Bmax of 14.8 fmol/10(7) cells; the low affinity sites have a Kd of 0.58 microM and a Bmax of 2453 fmol/10(7) cells. The appearance of specific leukotriene B4 binding sites in the myeloid differentiated cells correlates with their ability to chemotax in response to leukotriene B4. Undifferentiated cells do not chemotax to leukotriene B4. At 37 degrees C leukotriene B4 is incorporated into phospholipid and triglyceride species in both undifferentiated and myeloid differentiated HL-60 cells making binding studies at 37 degrees C in intact cells impossible. No evidence of omega-hydroxylase activity was found in HL-60 cells. These data suggest that the HL-60 cell may be an excellent model system for the study of leukotriene B4 receptor binding, processing, and gene expression. |
