Comparison of bisretinoid levels in cyclic light-reared and dark-reared albino Abca4−/− mice. (A and B) Representative reverse-phase chromatograms with 430-nm monitoring to detect A2E (1) and iso-A2E (13–14 cis) (2), A2-GPE (3), A2-DHP-PE (4), and all-trans-retinal dimer-PE (atRAL dimer-PE) (5) in dark-reared (A) and cyclic light-reared (B) albino Abca4−/− mice (8 mo). (Insets) Chromatograms expanded between retention times 44–47 min. (C) UV-visible absorbance spectra of the indicated compounds. (D) Quantitation of bisretinoid compounds in albino Abca4−/− mice (6 mo) that were cyclic-light or dark-reared; picomoles of A2E and iso-A2E were summed. A2E, A2-DHP-PE, atRAL di-PE were quantified by HPLC, and A2-GPE was quantified by UPLC. Mean ± SEM of two to five samples, four to six eyes per sample; P values determined by one-way ANOVA and Sidak’s multiple comparison test.