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PubMed1981

Chromosomal analysis in vinyl chloride exposed workers: comparison of the standard technique with the sister-chromatid exchange technique.

A group of 21 workers occupationally exposed to vinyl chloride and 6 controls were examined for the presence of chromosomal aberrations or sister-chromatid exchanges in their peripheral lymphocytes. These people comprised a second sampling from a group of exposed workers and controls first examined 18 months earlier. The vinyl chloride exposed workers showed levels of chromosomal aberrations elevated above those of the controls, but there was only a slight increase in sister-chromatid exchanges (per cell or per chromosome) and this increase was not statistically significant. Sister-chromatid exchanges (SCEs) were also examined from in vitro cultures of lymphocytes exposed in G0/early G1 and late G1/early S phase to vinyl chloride, both with and without metabolic activation. There was no increase in SCEs in vitro without metabolic activation but there was a marked increase with metabolic activation and this increase was shown to be independent of cell-cycle phase. It thus was apparent that the small increases of SCEs in workers were not due to the inability of vinyl chloride to induce SCEs in human lymphocytes but were probably because of low exposures and SCE levels could have returned to normal relatively quickly after exposure. The present study suggested that the analysis of longer-living conventional chromosomal aberrations appeared to be a more sensitive monitor of exposure to vinyl chloride in exposed workers than the estimation of SCEs; however, it should be noted that in a 3rd sampling taken 24 months later the exposed workers had chromosomal aberration levels similar to the controls.

Cells, Cultured↗
PubMedDate not supplied

Induction of chromosome aberrations by styrene and vinylacetate in cultured human lymphocytes: dependence on erythrocytes.

Two vinyl monomers, styrene and vinylacetate, were tested for their ability to induce chromosome aberrations in cultured human lymphocytes. The effects of a 24-h treatment (48 h after culture initiation) were studied both in whole-blood cultures (with 2 X 10(8) erythrocytes/ml) and in isolated lymphocytes (with 4000 erythrocytes/ml). Styrene produced a clear dose-dependent increase in chromatid-type aberrations in whole-blood cultures (0.5-6 mM) and a weaker effect in cultures of isolated lymphocytes (1-4 mM). A statistically significant elevation in aberrations was observed at 2 mM in the former culture type and at 1 mM in the latter. These results support earlier studies on the importance of erythrocytes in the metabolic activation of styrene, but also suggest that a part of this activation occurs in the lymphocytes themselves. Vinylacetate (0.125-2 mM), the more potent clastogen of the two monomers tested, induced a distinct dose-dependent increase in chromatid-type aberrations and a slight elevation in chromosome-type breaks in both culture types. The lowest concentration giving a positive result was 0.25 mM. The clastogenic effects of vinylacetate were somewhat more pronounced in isolated lymphocytes than in whole blood. Vinylacetate is known to be rapidly hydrolyzed in vitro to acetaldehyde, which probably explains the positive result.

Biotransformation↗
PubMed1989

Nucleophilic selectivity as a determinant of carcinogenic potency (TD50) in rodents: a comparison of mono- and bi-functional alkylating agents and vinyl chloride metabolites.

Using published data, the carcinogenic potency (TD50) in rodents of a series of monofunctional alkylating agents, bifunctional antitumor drugs and the vinyl chloride (VC) metabolites chloroethylene oxide (CEO) and chloroacetaldehyde (CAA) was compared to their nucleophilic selectivity (Swain and Scott's constant s or initial ratio of 7-/O6-alkylguanine in DNA). A positive correlation between the log of TD50 estimates and the s values for a series of 14, mostly monofunctional, alkylating agents was observed. This linear relationship also included 2 bifunctional chloroethylnitrosoureas, although their carcinogenic potency was compared to their initial 7-/O6-alkylguanine ratio rather than their s values (n = 16, r = 0.91, p less than 0.005). In addition, the carcinogenic potency of 2 alkyl sulfates, which is not yet known accurately, may correlate with their nucleophilic selectivity through the same relationship. By contrast, 2 methyl halides and 5 bifunctional antitumor drugs (nitrogen mustards and azyridinyl derivatives) did not follow this linear relationship: at similar nucleophilic selectivity, they were more potent carcinogens than the above 18 alkylating agents; this may hold true for CEO and CAA too, although further carcinogenicity experiments are needed to calculate their precise TD50 values. The possible molecular mechanisms involved in tumor induction by these agents are discussed on the basis of these findings. Comparison of the estimated TD50 for CEO, CAA and VC in rodents confirms that CEO is the ultimate carcinogenic metabolite of VC and suggests that only a very small proportion of metabolically generated CEO is available for DNA alkylation in vivo.

Alkylating Agents↗
PubMed1994

Direct and carbonylative vinylation of steroidal triflates in the presence of homogeneous palladium catalysts.

The palladium-catalyzed vinylation of several steriod 2-enyl- and 3,5-dienyl-3 triflates and estrone-3-triflate was systematically examined using vinyltributylstannane as a vinylating agent. In carbon monoxide atmosphere the insertion of a CO molecule took place and unsaturated ketones were obtained. In this way new steroid derivatives containing unsaturated side chain were produced, which can serve as starting material for further functionalization of the steroid skeleton.

Androstenes↗