The requirement of Zn2+ for the increase in ornithine decarboxylase induced by insulin and epidermal growth factor in primary cultured rat hepatocytes

IN-AIR MICRO-PIXE ANALYSIS FOR METAL ELEMENTS IN RAT HEPATOCYTES TREATED WITH FUCOIDAN

This study was undertaken to elucidate physiological properties of fucoidan extracted from Cladosiphon okamuranus TOKITA (C. okamuranus) and Fucus vesiculosus (F.vesilurosus). According to the data on MTT assay and TUNEL staining, F. vesiculosus possessed more anti-proliferate activity than C. okamuranus through apoptosis induction. We determined the metal contents of fucoidan to evaluate the relevance of metal elements in its biological effects. Al , Fe and Zn levels were significantly increased in F. vesiculosus than in C. okamuranus. The intracellular changes of metal elements following the administration of fucoidan was analyzed by in-air micro-PIXE in TRL1215 cells (normal rat liver cell line). At 24 h after 5-bromo-2'-deoxyuridine ( BrdU ) dosing, TRL1215 cells were treated with 1.0 mg/mL of each fucoidan for 9 h. The X-ray spectra showed that F. vesiculosus-treated cells markedly increased the yield of aluminum ( Al ) compared to those of C. okamuranus -treated cells and the control. In F. vesiculosus -treated cells, the focal accumulation of Br was spatially correlated with Al map, suggesting that Al was localized within the nucleus. These findings suggest that F. vesiculosus fucoidan increases the accumulations of Al in rat hepatocytes, which may participate in anti-proliferate activity of this fucoidan.

Restricted Zn2+ availability affects the antizyme-dependent ornithine decarboxylase degradation pathway in isolated primary cultured rat hepatocytes

We previously reported that lack of Zn2+ decreased ornithine decarboxylase (ODC) activity without any change in ODC messenger RNA levels and the half-life of ODC activity being about 2-fold more rapid in primary cultured adult rat hepatocytes, suggesting that lack of Zn2+ decreased ODC activity mainly by degrading the enzyme. The present investigations showed that the chelator, diethylenetriamine penta-acetic acid (DTPA), increased the ratio of ODC-antizyme complex to total ODC (about 2-fold) and caused a decrease in antizyme inhibitor, a protein inhibitor of ODC antizyme (about 50%). These results indicate that a restricted Zn2+ availability affects the antizyme-dependent ODC degradation pathway and consequently decreases ODC activity in primary cultured rat hepatocytes.