The uptake and release of benzo[a]pyrene and benzo[e]pyrene in vitro by Syrian hamster embryo cells as a function of serum concentration

Binding and uptake of N-nitrosonornicotine by oral epithelial cells

N-nitrosonornicotine (NNN), a significant nitrosamine component of tobacco binds to and is taken up by cells prior to its activation by intracellular enzymes. A variety of factors may affect the binding of substances to a cell including the cell type, medium composition and the cell membrane lipid composition. This study examines the binding and uptake of NNN to various cell types and relates these to the cells' lipid composition. Hamster buccal pouch keratinocytes were exposed to NNN and the amount of bound NNN determined. This was compared with cells pretreated with 12-0-tetradecanoylphorbol-13-acetate (TPA). While the keratinocytes bound significant amounts of NNN, this binding was not specific. Pretreatment of the cells with TPA significantly increased the amount of NNN bound. Cultures of human gingival fibroblasts and a human liver cell line also bound NNN, in quantities greater than that bound to the keratinocytes. The TPA caused changes in long chain unsaturated fatty acids although major changes in lipid metabolism were not detected. The fatty acid composition of the liver cells more closely resembled that of the TPA treated keratinocytes than the untreated ones. The data suggest that NNN binds to the cells non-specifically and the binding may be related to the amount of long-chain, unsaturated fatty acids present.

Micronuclei in red blood cells of the newt Pleurodeles waltl after treatment with benzo(a)pyrene: dependence on dose, length of exposure, posttreatment time, and uptake of the drug

Aquatic larvae of the newt Pleurodeles waltl were exposed to different concentrations of benzo(a)pyrene (BaP) for various lengths of time. Frequencies of micronuclei in circulating erythrocytes were determined at different times after termination of the treatment. The incidence of micronuclei in larvae kept for 8 days in BaP-containing water displayed a marked increase with dose up to 0.075 ppm and a more gradual one with higher doses, reaching 158 per 1,000 at 0.75 ppm. The lowest dose at which a significant increase could be discerned was 0.01 ppm. Short periods of exposure, less than 2 days, did not result in a marked increase in micronuclei. Uptake and release was studied with tritiated BaP. Larvae concentrated BaP rapidly, attaining maximal levels after 12 hr. The ratio of radioactivity in larvae to that in an equivalent volume of surrounding water was about 200 independent of the amount of BaP added. Calf serum or bovine serum albumin added to the water lowered this ratio by competing for binding to BaP. Radioactive larvae placed in regularly renewed noncontaminated water lost 99% of the label after 100 hr. It is concluded that pleurodele larvae are a promising model for the detection of genotoxic activity in the aquatic environment.

Effect of serum concentration on the cytotoxicity and sister chromatid exchange induction by a chemical carcinogen and by a diesel particulate extract in V79 hamster cells

The role of serum concentration on the cytotoxicity and on the sister chromatid exchange (SCE)-induction by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and by a diesel particulate extract (DPE), a complex mixture, has been carried out on V79 cells. An increase of the serum concentration in the medium decreases the toxicity of these chemicals, and especially when they are dispersed first in serum. Although no influence of serum concentration on the number of spontaneous SCEs occurring in control cells has been observed, the increase of serum concentration leads to a decrease in SCE's induction in treated cells. Our results show that serum can protect cells from the cytotoxic and mutagenic action of MNNG and diesel extract.