metallothionein and 4-aminopyrazolo(3-4-d)pyrimidine

To examine intranuclear localization of metallothionein (MT) induced by administration of 4-aminopyrazolo [3,4-d] pyrimidine (4-APP), the present study of MT was performed by immuno-electron microscopy. One day after oral administration of 4-APP, the mouse pancreas removed and frozen with dry ice was cut at about 1 mm thickness. Pancreatic slices were reacted with anti-MT antibody, fixed with formaldehyde and glutaraldehyde, and embedded in hydrophilic Lowicryl K4M resin. Ultrathin sections were reacted with the secondary antibody labelled with colloidal gold, and stained both with uranyl acetate and with lead citrate. It was found that the MT site was shown simultaneously in the chromatin and in the rough endoplasmic reticulum of mouse pancreatic exocrine cells one day after administration of 4-APP. The structure of MT-binding chromatin was composed of supranucleosomal fibers, but not of nucleosomal fibers.

Topics: Adenine; Animals; Cell Compartmentation; Cell Nucleus; Endoplasmic Reticulum, Rough; Enzyme Induction; Metallothionein; Mice; Mice, Inbred Strains; Microscopy, Immunoelectron; Nucleosomes; Pancreas; Protein Binding

Pancreatic metallothionein (MT) and zinc levels were measured after the administration of 4-aminopyrazolo(3,4-d)pyrimidine (4APP) to mice to determine the role of pancreatic MT. 4APP was found to increase the pancreatic MT level dose-dependently; the pancreatic MT level in mice administered 175 mg/kg of 4APP was 3.9 fold higher than that in control mice. When 40 mg/kg or less of 4APP was administered, the zinc concentration of the pancreatic cytosol fraction did not differ from that in control mice, while after 175 mg/kg of 4APP it was 1.7-fold higher. There was no difference in plasma glucose and insulin levels between the controls and mice administered 175 mg/kg of 4APP, although the plasma alpha-amylase activity was reduced in the latter. Moreover, a linear negative relationship was observed between pancreatic MT level and plasma alpha-amylase activity (r = -0.795, p < 0.01). These findings suggest that pancreatic MT is affected by the disruption of the exocrine function in 4APP-administered mouse pancreas.

Topics: Adenine; alpha-Amylases; Animals; Anticholesteremic Agents; Dose-Response Relationship, Drug; Insulin; Male; Metallothionein; Mice; Pancreas; Zinc