FIGURE 3.

UV treatment decreases endogenous retinoids to below HPLC-detectable levels, whereas exogenously added retinoids are confirmed to penetrate tissue. A, one retina was taken from each of eight P8-P10 animals, frozen, and later assayed by HPLC for endogenous retinoids levels. B, the contralateral retina from each animal in A was exposed to 15 min of UV light, frozen, and assayed by HPLC. No retinoids were detected after UV treatment. The remaining chromatograms show retinoid levels from retinas taken after UV exposure and subsequent treatment with vehicle (n = 3) (C), 100 μm 9-cis-retinal (n = 4) (D), and 100 μm all-trans-retinal (n = 7) (E).