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Chapter 54

Differences in Photoreceptor Sensitivity to Oxygen Stress Between Long Evans and Sprague-Dawley Rats

Vicki Chrysostomou, Jonathan Stone, and Krisztina Valter

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.

54.1 Introduction

It has long been known that hyperoxia is specifically toxic to photoreceptors (Noell 1955). Elevation of the partial pressure of oxygen in the retina results in photoreceptor degeneration that increases as a function of time (Yamada et al. 1999; Okoye et al. 2003; Geller et al. 2006) and oxygen concentration (Wellard et al. 2005). The vulnerability of photoreceptors to hyperoxia is a result of the unique architecture of oxygen delivery to the outer retina. The outer retina lacks intrinsic blood vessels;

V. Chrysostomou (B)

Research School of Biological Sciences, The Australian National University, Canberra, Australia e-mail: vicki.chrysostomou@anu.edu.au

R.E. Anderson et al. (eds.), Retinal Degenerative Diseases, Advances in Experimental

473

Medicine and Biology 664, DOI 10.1007/978-1-4419-1399-9_54,C Springer Science+Business Media, LLC 2010