Differences in photoreceptor sensitivity to oxygen stress between Long Evans and Sprague-Dawley rats

Abstract

Purpose: To examine the susceptibility of photoreceptors to hyperoxic stress in two rat strains, the pigmented Long Evans (LE) and the albino Sprague-Dawley (SD). Methods: Adult LE and SD rats were exposed to hyperoxia (75% oxygen) for 14 days. Retinas were assessed for electroretinogram (ERG) responses, cell death, and expression of a retinal stress factor. Results: In the LE strain, exposure to hyperoxia significantly reduced amplitudes of rod a-wave, rod b-wave and cone b-wave components of the ERG, and caused a 55-fold increase in photoreceptor cell death rates, and an upregulation of GFAP expression. In the SD strain, hyperoxic exposure had no measurable effect on the ERG response of rods or cones, and resulted in a modest (5-fold) increase in the rate of photoreceptor cell death. Conclusions: In LE and SD strains, hyperoxia induces cell death specific to photoreceptors. The effect is an order of magnitude more severe in the pigmented LE strain suggesting a strong genetic component to oxygen sensitivity, as reported previously between the albino Balb/C and pigmented C57BL/6 strains of mice.