ABSTRACT
To understand the expression of hoth TGF-beta l and II ligands and the receptors, artificial fracture was made on rat femur. Fracture callus and epiphyseul plate were stained immunohistochemically on 3rd. 7th, 14th, 21st, 42nd and 56th day after trauma. Polyclonal antibody was used to stain TGF-beta I and II ligands and receptors. At epiphyseal plate, both ligand and receptor were expressed from each cell in proliferating and maturing zone. But there was no difference between type I and II except expression time. TGF-beta II ligand and receptor were expressed earlier: they were expressed mostly by the cells at the zone of proliferating cartilage but TGF-beta1 ligand and receptor were expressed mostly hy the cells at zone of maturing cartilage. At fracture site, TGF-beta expression was observed from 3rd day after trauma and it reached its maximum intensity at 2 weeks. It decreased thereafter and disappeared at 6 weeks after trauma. In enchondral ossification area, TGF-beta expressing cells were scattered throughout the enchondral mass. In intramembranous ossification area, the ligands and receptors were expressed from the osteohlasts just heneath the periosteum. ln summary, TGF-beta ligands and receptors were expressed at epiphyseal plate and fracture callus. There was no difference between TGF-beta 1 and 2 expres.ion except the appearance time at epiphyseal plate. We could not draw any conclusion about ligand and rcceptor mechanism with this immunohistochemical staining.
Subject(s)
Animals , Rats , Bony Callus , Cartilage , Femur , Growth Plate , Ligands , Periosteum , Receptors, Artificial , Transforming Growth Factor beta , Transforming Growth Factor beta1ABSTRACT
We attempted to study the role of protein tyrosine kinase (PTK) and protein kinase C (PKC) in the cascade of phosphorylation of ribosomal protein S6 during differentiation of leukemic cells (HL-60, THP-1, and RWLeu-4). Neither activation nor inhibition of colony stimulating factor-1 (CSF-1) receptor's PTK activity with CSF-1 or genistein respectively affected the phosphorylation of S6. However, vanadate which is a protein tyrosine phosphatase (PTP) inhibitor showed enhancement of S6 phosphorylation. Dimethylsulfoxide which does not affect either PTK or PKC demonstrated no change in S6 phosphorylation. PKC activation by acute 12-0-tetradecanoyl phorbol-13-acetate (TPA) treatment induced monocytic differentiation and S6 phosphorylation. Surprisingly, the more prominent phosphorylation of S6 protein was observed in PKC-depleted cells by prolonged TPA treatment. Our results suggest that PTK/PTP play a lesser role in S6 phosphorylation of HL-60 cells than PKC does. In addition, two different mechanisms seem to be involved in TPA-induced S6 phosphorylation during HL-60 differentiation: PKC activation by acute TPA treatment and PKC depletion which may lead to the synthesis of some endogenous protein responsible for the differentiation by chronic TPA treatment.