Figure 4. Normalized expression of reference genes in rat retinal cDNA pools

Gene expression in each pooled sample was normalized by dividing the relative expression value by the geometric mean of the expression levels of the two selected reference genes, acidic ribosomal phosphoprotein (ARBP) and hypoxanthine guanine phosphoribosyltransferase (HPRT), in the same sample. There was little variation between groups for the normalized expression of ARBP (A) or HPRT (B). In contrast, the expression of RNA polymerase 2 (RNAP2; C) varied considerably between groups: Within each strain, expression was higher in the oxygen exposed group (O14), than in the room air group (RA). In the figure, n=6 replicates per experimental group of three pooled rat retinas and error bars equal ±SD. The following abbreviations were used: Sprague Dawley (S) Fischer 344 (F), Dark Agouti (D), room air raised, day 14 (R14), and cyclic hyperoxia exposed, day 14 (O14).