Exceptional sensitivity of mink to the hepatotoxic effects of dimethylnitrosamine

Risk assessment of N-nitrosamines in food

EFSA was asked for a scientific opinion on the risks to public health related to the presence of N-nitrosamines (N-NAs) in food. The risk assessment was confined to those 10 carcinogenic N-NAs occurring in food (TCNAs), i.e. NDMA, NMEA, NDEA, NDPA, NDBA, NMA, NSAR, NMOR, NPIP and NPYR. N-NAs are genotoxic and induce liver tumours in rodents. The in vivo data available to derive potency factors are limited, and therefore, equal potency of TCNAs was assumed. The lower confidence limit of the benchmark dose at 10% (BMDL10) was 10 μg/kg body weight (bw) per day, derived from the incidence of rat liver tumours (benign and malignant) induced by NDEA and used in a margin of exposure (MOE) approach. Analytical results on the occurrence of N-NAs were extracted from the EFSA occurrence database (n = 2,817) and the literature (n = 4,003). Occurrence data were available for five food categories across TCNAs. Dietary exposure was assessed for two scenarios, excluding (scenario 1) and including (scenario 2) cooked unprocessed meat and fish. TCNAs exposure ranged from 0 to 208.9 ng/kg bw per day across surveys, age groups and scenarios. 'Meat and meat products' is the main food category contributing to TCNA exposure. MOEs ranged from 3,337 to 48 at the P95 exposure excluding some infant surveys with P95 exposure equal to zero. Two major uncertainties were (i) the high number of left censored data and (ii) the lack of data on important food categories. The CONTAM Panel concluded that the MOE for TCNAs at the P95 exposure is highly likely (98-100% certain) to be less than 10,000 for all age groups, which raises a health concern.

Diagnosis of liver disease in domestic ferrets (Mustela putorius)

Liver disease in ferrets is often subclinical and underdiagnosed. Clinical pathology and diagnostic imaging are needed to guide clinicians but definite diagnosis is based on histopathologic lesions. Inflammatory digestive conditions can lead to ascending tract infection and hepatobiliary inflammation. Ferrets have a specific sensitivity to hepatic lipidosis. Incidence of hepatic neoplasia is high in ferrets. After a summary of anatomy and physiology of the ferret liver, hepatic diseases known in ferret species are reviewed with their subsequent diagnostic procedures.

Studies on the mechanism of the acute and carcinogenic effects of N-nitrosodimethylamine on mink liver

Outbreaks of liver necrosis and liver hemangiosarcoma were detected in a mink breeding colony in Argentina. Analysis of the Minks' food revealed the presence of 2.6 ppm dimethylnitrosamine (NDMA) in it, apparently as a result of the addition of nitrite as preservative. Previous studies gave evidence of the particular susceptibility of minks to NDMA and other hepatic insults. We have determined several biochemical parameters known to correlate with NDMA hepatotoxic effects and compared them with those in rat liver. NDMA administration to both species resulted in the formation of reactive metabolites able to interact with liver DNA to give N7-methylguanine and O6-methylguanine adducts. Biotransformation of NDMA by liver slices to CO2 was significantly lower in the mink than in the rat, whereas the covalent binding (CB) to nucleic acids was slightly lower than in in the rat. Aminopyrine N-demethylase activity was also significantly less in mink than in rat liver. The CB of NDMA reactive metabolites to microsomal proteins was not significantly lower in mink as compared to the rat, and the same holds true for the biotransformation of NDMA to formaldehyde by microsomal preparations. Results suggest that the high susceptibility of minks to NDMA might be partially due to a decreased ability to detoxicate NDMA but also to a higher intrinsic susceptibility of their liver cells to a given chemical insult.

Hepatotoxicity of dimethylnitrosamine in cats and lizards

The hepatotoxic effects of the oral administration of a single dose of 50 mg dimethylnitrosamine (DMN)/kg and daily doses of 5 mg and 1 mg/kg, respectively, to cats and lizards were studied by light microscopy. Centrilobular necrosis was the main alteration detected in the liver of cats as in other animal species studied. The lizards, however, appeared unaffected. Morphological changes observed in the liver of these reptiles included haemorrhage, vacuolation of hepatocytes and diffuse nuclear changes; including pyknosis, karyorrhexis and karyolysis. Haemorrhage was also evident in the liver of cats as well as leukocytic infiltration;. including macrophages, lymphocytes and neutrophils. Cats appeared to be more susceptible to DMN poisoning.

[Pathogenesis of aleutian mink disease. VII. Chronic hepatitis with bile duct proliferation]

Aleutian disease is a chronic persistent viral infection of mink characterized by hypergammaglobulinema, generalized plasmacytosis, sclerosing glomerulonephritis, polyarteritis, and plasma cell hepatitis with bile duct proliferation. The development of hepatic lesions was studied both light- and electron-microscopically in mink experimentally infected with Aleutian disease virus. Fifteen normal and 99 mink experimentally infected with Aleutian disease virus were used. Experimental mink were killed in intervals from 3 weeks to 23 months after infection, and liver sections were processed for both light- and electron-microscopic studies. Experimentally infected mink developed portal and intralobular lymphocytic and plasmacytic infiltrates in the liver 3 weeks after infection. Four to five weeks after infection there was evidence of early bile duct proliferation that began as an outgrowth of the portal bile ducts. Three to five months after infection a marked bile duct proliferation was present in some of the portal triads and adjacent liver lobules; but there was no tendency of these lesions to progress into biliary cirrhosis. Ultrastructural characteristics of proliferating bile duct cells were marked deformation, formation of multiple cell layers, reduction in the number of microvilli and desmosomes, and infiltration of the epithelial cells by lymphoid cells and plasmacytes. The hepatic lesions either develop by direct virus stimulation or by the deposition of virus-antibody complexes.