Mouse liver effects of cyproconazole, a triazole fungicide: role of the constitutive androstane receptor.

Cyproconazole, a triazole fungicide, causes hepatocellular adenomas and carcinomas in CD-1 mice at dose levels of 100 and 200 ppm. The constitutive androstane receptor (CAR) has been shown to play a significant role in the overall mode of action for several nongenotoxic rodent carcinogens such as phenobarbital. The liver effects of dietary cyproconazole or phenobarbital were investigated after 2, 7, or 14 days in male CD-1, C57BL/6J, and C3H/HeNClrBR mice.

Thiamethoxam induced mouse liver tumors and their relevance to humans. Part 1: mode of action studies in the mouse.

Thiamethoxam, a neonicotinoid insecticide, which is not mutagenic either in vitro or in vivo, caused an increased incidence of liver tumors in mice when fed in the diet for 18 months at concentrations in the range 500 to 2500 ppm. A number of dietary studies of up to 50 weeks duration have been conducted in order to identify the mode of action for the development of the liver tumors seen at the end of the cancer bioassay. Both thiamethoxam and its major metabolites have been tested in these studies.

Thiamethoxam induced mouse liver tumors and their relevance to humans. Part 2: species differences in response.

Thiamethoxam is a neonicotinoid insecticide that is not a mutagen, but it did cause a significant increase in liver cancer in mice, but not rats, in chronic dietary feeding studies. Previous studies in mice have characterized a carcinogenicity mode of action that involved depletion of plasma cholesterol, cell death, both as single cell necrosis and as apoptosis, and sustained increases in cell replication rates. In a study reported in this article, female rats have been exposed to thiamethoxam in their diet at concentrations of 0, 1000, and 3000 ppm for 50 weeks, a study design directly comparable to the mouse study in which the mode of action changes were characterized.