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L Zheng, JC Merriam, A Spector, NL Kleiman, J Dillon; Absorption of Light by the Lens Epithelial Cell Layer . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3579.
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Purpose: Numerous studies have demonstrated that the epithelial layer of the lens is damaged by the absorption of ultraviolet radiation. It was therefore of interest to determine what cellular components absorb light. Methods: The absorption spectra of cultured mouse and human epithelial cells, grown on a quartz plate, were determined using a PC 2000 Fiber Optic Spectrometer (Ocean Optics, Inc.). The system employs the continuous output of a deuterium lamp (ca. 200-700 nm) as the excitation source and a high sensitivity CCD detector mounted on a card, which is installed in a PC. The absorption spectrum of the epithelial cells was analyzed by principle component analysis. The relative number of photons absorbed by each component was then determined by multiplying the transmission of the cornea by the absorption spectra of each component and then integrating the resultant peaks using Origin 6.0. Results: Our studies gave the following results: 1) the maximum absorption of mouse lens epithelial cells was at 260 nm with an average optical density of 0.25-0.33 OD (seven samples). 2) The ratio of 260/280 nm gave 1.47, which suggests the presence of considerable cellular protein. 3) Multi-component analysis of the epithelial absorption spectrum gave two peaks at 260 and 280 nm, with the DNA peak absorbing some 3 times that of protein. 4) When the spectra were corrected for light actually transmitted by the cornea, however, each gave a maximum at ca 300 nm, with protein absorbing 1.8 times that of DNA. Conclusion: Although these studies rely in part on mathematical analysis of absorption spectra these results strongly suggest that that components other than DNA may initiate light damage in the epithelial cell layer.
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