The effect of aflatoxin B, on the maturation of ribosomal and transfer RNA in monkey kidney (CV-1) cells in culture

Synthesis of transfer RNA in rat liver after acute and chronic aflatoxin B1 administration

Synthesis of rat liver tRNA following acute and chronic administration of aflatoxin B1 was compared to protein synthesis. Twenty hours after acute administration of aflatoxin B1 total RNA synthesis was inhibited by 91% and tRNA synthesis by 77% while protein synthesis as assayed in vitro was inhibited by 75%. In the chronic (long-term) experiment at 7, 18 and 30 weeks after administration of aflatoxin B1 no inhibition of total RNA and tRNA synthesis was observed but protein synthesis in the cell-free system was inhibited by 16%. Thus, the inhibitory effects on protein synthesis observed in the long-term experiments are not correlated with the inhibition of tRNA synthesis.

Inhibitory effects of methyl glyoxal on DNA, RNA and protein synthesis in cultured guinea pig keratocytes

The inhibitory action of methyl glyoxal upon protein, RNA and DNA synthesis in guinea pig keratocytes has been investigated. Methyl glyoxal directly inhibits each of these processes. Inhibition of protein synthesis results from an action upon initiation of translation. Methyl glyoxal induces polysome degradation which is prevented by pretreatment with cycloheximide. Further analysis of translation indicates that elongation and termination are not affected. Inhibition of ribosomal RNA synthesis results from inhibition of maturation. Methyl glyoxal was found to inhibit the appearance of 28S rRNA in the cytoplasm from pulse-labelled precursors. The significance of these results is discussed in relation to cell injury by ketals.

Modification of the cytotoxicity of aflatoxin B1 in rat liver cells by steroids

The addition of steroids with aflatoxin B1 (AFB1) to rat liver cells in culture has been shown to increase the toxin's inhibitory action on growth and protein synthesis. In contrast the inhibition of RNA synthesis by AFB1 was unaffected. The steroid potentiates the direct action of AFB1 at initiation of translation.

Effects of dietary copper on developing aflatoxicosis in Syrian hamsters

The possible suppression of toxic and carcinogenic activities of aflatoxin by the cupric ion were investigated. Weanling, male Syrian hamsters received diets of either ground meal, ground meal plus 22.9 ppm mixed aflatoxins (9.2 ppm AFB1, 0.4 ppm AFB2, 12.8 ppm AFG1, 0.5 ppm AFG2), ground meal plus copper acetate (0.5% by weight) and 22.9 ppm mixed aflatoxins, or ground meal plus copper acetate (0.5%). Experimental parameters measured included: food and water consumption, body weight responses, mortality, gross pathology and histopathological changes, as well as protein synthesis in the liver tissue during incubation in Krebs' medium. The results indicate that copper may act as a protective agent against low levels of these mycotoxins. Significantly, more animals undergoing combined treatment (aflatoxin plus copper) survived and had higher body weights. Less severe liver pathology was seen in these animals as compared to those receiving aflatoxin without a copper supplement.

The effect of aflatoxin B1 on translation in cells in culture

The effect of aflatoxin B1 (AFB1) upon translation has been studied in two cell lines in culture, which differ markedly in their sensitivity to the toxin. It was found that AFB1 predominantly inhibits initiation of translation in both cell lines.

The relationship between the turnover of UTP and RNA synthesis in cultured cells treated with aflatoxin B1

Methods have been adapted to measure the specific activity of UTP in cells in monolayer culture. In HeLa cells labelled with [3H]uridine and treated with aflatoxin B1 there was reduced radioactivity in crude acid extracts, but the toxin did not affect the radioactive incorporation into UTP. Using cells in which the UTP was pre-labelled, the subsequent addition of aflatoxin B1 inhibited UTP incorporation into RNA. Accordingly aflatoxin B1 did not inhibit the uptake of uridine or the latter's conversion to UTP but inhibited the incorporation of UTP into RNA.