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AM Geller, L Perez, LD Sutton, RS Marshall, DL Hunter, RL Peiffer; Functional and Morphological Retinal Effects of the Organophosphorous Pesticide Chlorpyrifos in Rats . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2721.
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Purpose: There is concern that exposure to pesticides may comprise an environmental risk factor contributing to retinal degeneration. This study investigates long-lasting changes in retinal physiology and morphology in response to oral exposure to a cholinesterase-inhibiting pesticide. Methods: Adult male Long-Evans rats were fed the insecticide chlorpyrifos (CPF) in their diet at 0, 1, or 5 mg/kg body weight/day from 6 mos. of age for 1 year. In addition, half of each feeding group received an oral (spike) dose of CPF in corn oil (45 mg/kg) or corn oil alone every two months, resulting in six exposure groups: Control-Oil, Control-CPF, Low-Oil, Low-CPF, High-Oil, and High-CPF. Rats were 20-24 months old at testing. Dark-adapted ERGs and VEPs were recorded after recovery from the acute effects of dosing. The kinetics of dark adaptation were also measured by determining the flash intensity needed to elicit a 40 µV b-wave at 3 min intervals after a bright bleach. Histopathological assessment and morphometric measurements were made on glutaraldehyde/paraformaldehyde fixed, one micron thick epon-embedded retinal tissues after functional assessment. Results: There were no significant differences between dose or spike groups in dark-adapted ERG parameters. Estimation of absolute threshold from VEPs similarly revealed no effects of exposure. Rats receiving the episodic oral spike of CPF showed a slowed recovery of dark-adapted sensitivity compared to rats receiving the corn oil spike. Preliminary histopathological/morphometric examination suggests retinal changes in the outer retina associated with dosing with CPF. Conclusion: This result suggests that exposure to CPF may result in altered retinal structure and function. The slowed dark adaptation, measured in aged rats and akin to effects seen in the dark adaptometry of aging humans and humans exposed to pesticides, may reflect alterations in the photoreceptor/retinal pigment epithelial interaction. This may be related to effects of pesticides on second messenger function in the retina. (This abstract does not necessarily reflect US EPA policy).
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