Non-linear relationships between aflatoxin B₁ levels and the biological response of monkey kidney vero cells.
Aflatoxin-producing fungi contaminate food and feed during pre-harvest, storage and processing periods. Once consumed, aflatoxins (AFs) accumulate in tissues, causing illnesses in animals and humans. Most human exposure to AF seems to be a result of consumption of contaminated plant and animal products. The policy of blending and dilution of grain containing higher levels of aflatoxins with uncontaminated grains for use in animal feed implicitly assumes that the deleterious effects of low levels of the toxins are linearly correlated to concentration. This assumption may not be justified, since it involves extrapolation of these nontoxic levels in feed, which are not of further concern. To develop a better understanding of the significance of low dose effects, in the present study, we developed quantitative methods for the detection of biologically active aflatoxin B₁ (AFB1) in Vero cells by two independent assays: the green fluorescent protein (GFP) assay, as a measure of protein synthesis by the cells, and the microculture tetrazolium (MTT) assay, as a measure of cell viability. The results demonstrate a non-linear dose-response relationship at the cellular level. AFB1 at low concentrations has an opposite biological effect to higher doses that inhibit protein synthesis. Additional studies showed that heat does not affect the stability of AFB1 in milk and that the Vero cell model can be used to determine the presence of bioactive AFB1 in spiked beef, lamb and turkey meat. The implication of the results for the cumulative effects of low amounts of AFB1 in numerous foods is discussed.
Foodborne Contaminants Research Unit, Agricultural Research Service, USDA, Albany, CA 94710, USA. reuven.rasooly@usda.gov
Reuven
R
Rasooly
Bradley
B
Hernlem
Xiaohua
X
He
Mendel
M
Friedman
D016604:Aflatoxin B1 / Q000302:isolation & purification / Q000633:toxicity*; D000821:Animal Feed; D000818:Animals; D002417:Cattle; D002470:Cell Survival / Q000187:drug effects; D002522:Chlorocebus aethiops; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D005506:Food Contamination / Q000032:analysis*; D005511:Food Handling; D005516:Food Microbiology; D057809:HEK293 Cells; D006801:Humans; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D008460:Meat / Q000382:microbiology*; D008892:Milk / Q000737:chemistry / Q000382:microbiology; D012756:Sheep; D014421:Turkey; D014709:Vero Cells
D016604:Aflatoxin B1