Use of L-929 cell line for phototoxicity assessment.

L-929 is an adherent type of mouse fibroblast cell line was known as an alternate test system for toxicity assessment. Its photosensitivity towards ultraviolet radiation (UVR) was studied under the exposure to various intensities of UVA, UVB and sunlight. MTT assay was used for cell viability under UVR alone or in combination with chlorpromazine. UVB intensity below 0.6mW/cm2 did not show phototoxicity till 150min (min) exposure. UVA intensity up to 1.5mW/cm2 for 180min exposure did not alter the cell viability, but at 2.0 and 3.0mW/cm2 showed reduced cell viability beyond 90 and 60min, respectively. Sunlight exposure showed a loss in cell viability beyond 60min. Chlorpromazine showed a dose dependent phototoxic response under UVA, UVB and sunlight exposure. The study suggests the suitability of L-929, as an in vitro test system for the phototoxicity, which was compared with NIH-3T3 cell line. Therefore, L-929 cell line may also be used for phototoxicity assessment. The system provides information regarding the lethality of higher intensities of UVR and its importance in view of increasing UV intensities on the earth's surface due to ozone depletion. Our results suggest that a small change in UVR intensity (especially UVB) in sunlight may increase the risk of phototoxicity.