Glycerol phosphate dehydrogenase in developing retina of normal and mutant mice

The specific activity of glycerol phosphate dehydrogenase (GPDH; E.C. 1.1.1.1.8) was determined in the retinas of C57BL/6J mice from 2 to 45 days after birth. Comparisons were made with age-matched mice congenic to C57BL/6J and homozygous for the autosomal recessive mutations for retinal degeneration (rd) and light ear (le). The total activity of GPDH in the developing retina was similar in each strain throughout development. However, following the loss of photoreceptor cells in the rdle mice, the specific activity of GPDH increased to approximately twice the level of that in the controls. These data suggest that GPDH is absent from the photoreceptor cells and that its expression in the remaining retinal cells is unaffected by the loss of the photoreceptor cells. Retinal GPDH does not exhibit the eight-to ten-fold increase seen during development of the brain, but instead remains essentially constant during this time period, and in adult animals the specific activity of GPDH in the retina is about 20-fold less than it is in the brain. Neither mouse retinal GPDH nor brain GPDH is affected by adrenalectomy, suggesting that they are not regulated by glucocorticoids. The major form of GPDH in the retina is distinct from the major form in mouse brain since immunotitration experiments demonstrated that 70-80% of retinal GPDH does not react with anti-GPDH IgG, whereas the reverse was true for the brain enzyme.