Effects of N-nitrosopyrrolidine and N-nitrosoproline on the incorporation of 3H-thymidine into the DNA of various organs of the mouse: tissue specificity and effects of ethanol consumption

DNA damage in the nasal passageway: a literature review

The purpose of this review is to provide a compilation of work examining DNA damage in the nasal cavity. There are numerous methods to identify and quantify damage to DNA and the diversity of methods and toxicologic endpoints is illustrated by the range of studies presented here. There are a large number of independent studies measuring endpoints in the upper respiratory tract; however, with regard to toxicant induced DNA damage in the nasal passageway, the effects of two compounds, 4-(N-Methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and formaldehyde (HCHO), appear to have been extensively characterized. The body of work on NNK and formaldehyde have provided insights into molecular mechanisms of DNA damage and repair and induced cell replication and its relationship to nasal cancer. With new technologies and molecular techniques, the sensitivity to enable evaluations of the minute quantities of nasal tissue available in test species and human biopsy impact the study of the nasal-toxicant interactions. As methods used to characterize DNA damage increase in sensitivity, the importance of both exogenous and endogenous sources of DNA damage, steady-state levels of cellular damage, repair, and resulting mutations, low-dose exposure assessments and inter-species extrapolation will become increasingly complex. Additional studies of DNA damage in the nasal passage will undoubtedly challenge future estimations of risk and impact what are perceived to be acceptable levels of exposure to known and predicted carcinogens. The aim of this paper is to provide to the interested scientist literature relevant to the effects of agents on nasal DNA, so that areas of insufficient information can be identified and used to further develop and expand the knowledge base for nasal DNA toxicant interactions.

Evidence for elevation of cytochrome P4502E1 (alcohol-inducible form) mRNA levels in rat kidney following pyridine administration

The effects of pyridine on renal cytochrome P4502E1 (CYP2E1) expression in rat have been examined by immunoblot and Northern blot analyses. Immunoblot analyses revealed that 2E1 protein levels were elevated from 1.4- to 4.6-fold following pyridine administration in a dose- and time-dependent manner. Northern blot analyses revealed that renal 2E1 poly(A)+ RNA levels increased from 1.4- to 3.8-fold following pyridine treatment and that these increases in 2E1 mRNA paralleled the dose- and time-dependent increases in 2E1 protein content. In contrast, hepatic 2E1 poly(A)+ RNA levels failed to increase following these same dosing regimens, suggesting that metabolic alterations, such as those associated with starvation, were not etiologic factors in renal 2E1 induction. These results show that pyridine induced CYP2E1 in kidney and that elevation of renal 2E1 protein levels accompanying pyridine administration occurred at least partly as a consequence of increased 2E1 poly(A)+ RNA levels. The results of this research reveal that regulatory mechanisms governing CYP2E1 expression may differ in hepatic and renal tissues.

Inhibitory effects of benomyl and carbendazim on the [3H]thymidine incorporation in various organs of the mouse--evidence for a more pronounced action of benomyl

The benzimidazole fungicides benomyl and carbendazim were compared with regard to effects on [3H]thymidine incorporation in various organs of male mice given the compounds orally at various time intervals before sacrifice. Since carbendazim is a major metabolite of benomyl, it is generally assumed that the fungicidal action and toxicity of these compounds are due to the action of carbendazim. However, whereas benomyl inhibited the [3H]thymidine incorporation into thymus, spleen, liver, kidney and testis, an equimolar amount (3.4 mmol/kg body wt) of carbendazim induced a similar effect only in testis.

Effect of o,p'-DDD on the in vivo incorporation of 3H-thymidine into DNA: evidence for induced cell proliferation in the mouse lung

The effects of o,p'-DDD on the DNA synthesis in the C57Bl mouse lung and liver were studied. As determined by 3H-thymidine incorporation into DNA, a selective increase in the lung DNA synthesis (+59%) was observed 2 days after a single intraperitoneal injection of 100 mg/kg o,p'-DDD. Microautoradiography showed that the incorporated 3H-thymidine was confined to a restricted number of heavily labelled cells, presumably proliferating type II cells. At the most, a 9 times higher rate of cell proliferation was observed in the lung 4 days after an intraperitoneal injection of 500 mg/kg o,p'-DDD. Using mouse lung or liver S-9 as activating system, no mutagenic activity of o,p'-DDD was detected in the Ames test. The induced cell proliferation may indicate a tissue-selective promoter activity of o,p'-DDD in the mouse lung.