Figure 3. Quantification of 11-cis retinal. Since approximately 97% of all available 11-cis retinal in the mouse eye is bound to rhodopsin, chromophore was indirectly quantified measuring rhodopsin levels in the retina-retinal pigment epithelium (RPE) fraction. A: Example of difference spectra for P18 retinas from dark-adapted intact animals and retinas grown in organ culture starting at postnatal day 7 maintained in complete darkness. B: The amounts of rhodopsin were quantified from wild-type littermates and retinal explants at different postnatal days. Explants contain approximately 40% of the amount of rhodopsin of the in vivo animals at P7+7DIV, and approximately 25% at the later age-group analysis. Data are represented as mean±standard deviation of three to four different sets of experiments.