| Abstrakt: |
The enzyme gamma-glutamyl transferase (GGT) is a multifunctional enzyme that participates in a number of metabolic processes, including the conversion of leukotriene C4(LTC4) to leukotriene D4(LTD4). LTD4 is necessary for normal myeloid proliferation and differentiation. We have examined the ability of hematopoietic growth factors (HGF) to induce GGT enzyme activity and mRNA content in a HGF-responsive cell line (KG-1). Incubation of KG-1 with recombinant human cytokines interleukin-1 beta (IL-1 beta), interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor (TNF), but not interleukin-6 (IL-6), granulocyte colony-stimulating factor (G-CSF) or monocyte colony-stimulating factor (M-CSF), results in significant increases in GGT enzyme activity. The increases in GGT activity are both dose- and time-dependent. In response to IL-1, increases in enzyme activity are seen by 6 hours and activity is maximal by 24 hours. GGT mRNA increases also occur and peak by 3 to 6 hours. These results indicate that induction of increases in GGT mRNA levels and enzyme activity occur in myeloid cells in response to HGFs. This induction, together with the requirement for LTD4 for normal granulopoiesis, supports a role for GGT in the cellular events occurring in myeloid cells in response to HGFs. |
