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Photoclastogenicity—an improved protocol, its validation, and investigation of the photogenotoxicity of DMBA
Author(s) -
Murli H.,
Aardema M.,
Lawlor T.,
Spicer C.
Publication year - 2002
Publication title -
environmental and molecular mutagenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1
H-Index - 87
eISSN - 1098-2280
pISSN - 0893-6692
DOI - 10.1002/em.10086
Subject(s) - clastogen , dmba , chinese hamster ovary cell , chemistry , ames test , carcinogen , salmonella , genotoxicity , chromatography , toxicology , toxicity , biology , bacteria , biochemistry , genetics , carcinogenesis , receptor , organic chemistry , gene
An improved protocol was developed to detect light‐induced clastogenic photoproducts in Chinese hamster ovary (CHO) cells. Dishes (60 mm) containing cells and the test material or vehicle control in 3 mL of phosphate‐buffered saline were exposed to light using a SUNTEST CPS solar simulation unit. Importantly, cells were exposed at about 25 cm from the light source, thereby allowing a short exposure time of 2 min. With this exposure the assay was conducted with lids removed during the UV exposure with minimal risk of contamination. After preliminary experiments an exposure of 165.6 mJ/cm 2 UVA: 17.0 mJ/cm 2 UVB was selected for treatments with the different phototoxins. Under these exposure conditions about 10–15% aberrant cells were induced in vehicle control cultures with no or minimal cytotoxicity. The well‐known photoclastogens 8‐methoxypsoralen (8‐MOP) and chlorpromazine (CLZ) were tested. In agreement with published data, 8‐MOP and CLZ were clastogenic (lowest observed effect level, LOEL, was 0.0159 μg/mL and 1.03 μg/mL, respectively). In the absence of UV, 8‐MOP was clastogenic at a much higher concentration (LOEL 251 μg/mL without UV vs. 0.0159 μg/mL with UV) while CLZ was negative up to a toxic concentration of 35 μg/mL. 7,12‐Dimethylbenz[a]anthracene (DMBA), which is photomutagenic in bacteria, was clastogenic at ≥0.005 μg/mL with UV light (without S9) and at ≥2.53 μg/mL with S9 (without UV light). These results demonstrate the utility of the protocol for the detection of photoclastogenicity and expand the characterization of DMBA's photogenotoxic activity. Environ. Mol. Mutagen. 40:41–49, 2002. © 2002 Wiley‐Liss, Inc.