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Positive correlation between pancreatic DNA damage and species specificity in response to
Abstract:
N-nitrosobis(2-oxopropyl)amine (BOP), a potent pancreatic carcinogen in hamsters that has failed to induce pancreatic tumors in rats, was studied for its effects on the DNA of both rat and hamster pancreas in order to relate DNA damage (as measured by alkaline elution) to carcinogenicity in vivo. At doses of 10, 20, and 40 mg BOP/kg, extensive DNA damage was detected in male Syrian golden hamster pancreas but Lewis rat pancreatic DNA was not affected. Only at doses of 100 mg BOP/kg or greater could pancreatic DNA damage in the rat be detected. DNA damage was also observed in both rat and hamster livers at 10, 20, and 40 mg BOP/kg. Alkaline elution analysis of DNA from isolated rat and hamster acinar cells treated in vitro with BOP revealed that only hamster acinar cell DNA was damaged. Rat acinar cell DNA was unaffected at all doses examined, up to 200 micrograms BOP/ml medium. Unscheduled DNA synthesis studies in cultured acinar cells confirmed the observations that BOP is genotoxic to hamster but not to rat acinar cells. The results strongly suggested that rat pancreas did not have the ability to metabolically activate BOP, which accounted for lack of both BOP-induced DNA damage and carcinogenicity in the rat.
Insights
N-nitrosobis(2-oxopropyl)amine (BOP) causes significant DNA damage in hamster pancreas but not in rat pancreas, explaining its carcinogenicity in hamsters and lack thereof in rats. This difference is linked to the rat pancreas's inability to metabolically activate BOP.
Area of Science:
- Toxicology
- Carcinogenesis
- Molecular Biology
Background:
- N-nitrosobis(2-oxopropyl)amine (BOP) is a known pancreatic carcinogen in hamsters.
- Rats are resistant to BOP-induced pancreatic tumors, necessitating investigation into the underlying mechanisms.
Purpose of the Study:
- To investigate the differential effects of BOP on pancreatic DNA in rats and hamsters.
- To correlate DNA damage with BOP's carcinogenicity in vivo and in vitro.
- To elucidate the role of metabolic activation in BOP's species-specific toxicity.
Main Methods:
- Alkaline elution assay to measure DNA damage in pancreatic and liver tissues from rats and hamsters treated with BOP.
- In vitro studies using isolated acinar cells from both species exposed to BOP.
- Unscheduled DNA synthesis assays in cultured acinar cells.
Main Results:
- BOP induced extensive DNA damage in hamster pancreas at lower doses (10-40 mg/kg) compared to rats.
- Rat pancreatic DNA damage was only observed at higher BOP doses (≥100 mg/kg).
- BOP caused DNA damage in the livers of both species, but only hamster acinar cells showed damage in vitro, indicating species-specific metabolic activation.
Conclusions:
- The rat pancreas lacks the metabolic capacity to activate BOP, explaining its resistance to BOP-induced DNA damage and carcinogenicity.
- Hamster pancreas can metabolically activate BOP, leading to genotoxicity and tumor formation.
- Differential metabolic activation is the key factor in the species-specific pancreatic carcinogenicity of BOP.