Metallothionein does not protect mouse endocrine cells from damage inducedby alloxan injection

Effects of metallothionein (MT) on pancreatic endocrine cells of mice, inje cted with alloxan and at different zinc status were studied. Mice were give n drinking water containing four different concentrations of zinc (0, 0.05, 0.1 or 0.5%) for 18 days, and alloxan was injected once on the 14th day. W hen zinc was added to the drinking water, pancreatic zinc and MT contents i ncreased after injection of alloxan, but did not change with injection of v ehicle alone, except in the group of mice drinking 0.5% zinc in water. Howe ver, plasma glucose level was increased in all the alloxan injected groups, and was independent of their zinc status. In mice given water with 0.5% of zinc, both pancreatic zinc and MT contents were higher than control mice g iven water alone. There was no difference in zinc and MT contents of the pa ncreas in mice drinking 0.5% zinc in groups injected with either alloxan or vehicle. The increase in plasma alpha-amylase activity, an indicator of pa ncreatic exocrine toxicity, was observed only in mice drinking water with 0 .5% zinc after injection of both alloxan and vehicle. Histochemically, degr anulation of zymogen and duct-like structures of exocrine cells and atrophy and disappearance of islet cells were observed in alloxan-injected mice dr inking 0.5% zinc in water. The zymogen degranulation was observed on the ve hicle-injected mice drinking 0.5% zinc in water. MT was immunohistochemical ly detected in the exocrine cells of both alloxan- and vehicle-injected mic e given 0.5% zinc in water. No MT was detected in islet cells of mice in an y group. The results show that an increase of zinc content may be followed by induction of MT synthesis in the pancreas of mice given increasing amoun ts of zinc in drinking water. However, MT dose not provide any protection a gainst damage caused by alloxan to endocrine cells of the pancreas. (C) 199 9 Elsevier Science Ireland Ltd. All rights reserved.