Metallothionein does not protect mouse endocrine cells from damage induced by alloxan injection.

Effects of metallothionein (MT) on pancreatic endocrine cells of mice, injected with alloxan and at different zinc status were studied. Mice were given 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. When zinc was added to the drinking water, pancreatic zinc and MT contents increased after injection of alloxan, but did not change with injection of vehicle alone, except in the group of mice drinking 0.5% zinc in water. However, 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 given water alone. There was no difference in zinc and MT contents of the pancreas in mice drinking 0.5% zinc in groups injected with either alloxan or vehicle. The increase in plasma alpha-amylase activity, an indicator of pancreatic exocrine toxicity, was observed only in mice drinking water with 0.5% zinc after injection of both alloxan and vehicle. Histochemically, degranulation of zymogen and duct-like structures of exocrine cells and atrophy and disappearance of islet cells were observed in alloxan-injected mice drinking 0.5% zinc in water. The zymogen degranulation was observed on the vehicle-injected mice drinking 0.5% zinc in water. MT was immunohistochemically detected in the exocrine cells of both alloxan- and vehicle-injected mice given 0.5% zinc in water. No MT was detected in islet cells of mice in any 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 amounts of zinc in drinking water. However, MT dose not provide any protection against damage caused by alloxan to endocrine cells of the pancreas.