Lack of involvement of metallothionein expression in pancreatic carcinogenesis by N-nitrosobis (2-oxopropyl) amine in Syrian hamsters.

The possible involvement of metallothionein (MT) in pancreatic ductal carcinogenesis by N-nitrosobis(2-oxopropyl) amine (BOP) in hamsters was investigated. Hamsters received subcutaneous (s.c.) injections with dissolved BOP to 70 mg/kg body weight (BW) followed 7 days later by 20 mg/kg BW BOP and they were sacrificed at 4, 11, 16 and 27 weeks after the beginning of the experiment. MT expression was studied by immunohistochemistry and MT contents were assayed biochemically. Pancreatic ductal hyperplasias were developed from 11 weeks on and carcinomas from 16 weeks on, the incidence of the latter reaching 73% at the end of experiment. However, while normal appearing proliferating duct cells were sometimes positive, MT expression was not evident in hyperplasia (H), atypical hyperplasia (AH) or carcinoma (C), and MT contents did not significantly differ in pancreas of hamsters receiving saline or BOP at any time point. The results suggest that MT is not involved in pancreatic duct carcinogenesis. However, the presence of MT in proliferating ducts not related to carcinogenesis may suggest some unknown role for MT in cellular homeostasis.