Effect of lutein and zeaxanthin supplementation on serum and tissue distributions in Abca4−/−/Bco2−/− and Abca4−/− mice supplemented for three months. The carotenoid distribution in (a) retina, (b) serum, (c) liver, and (d) brain shows significantly elevated levels of lutein and zeaxanthin in Abca4−/−/Bco2−/− mice. Mice fed lutein had exclusively lutein in all tissues. Mice fed zeaxanthin had exclusively zeaxanthin in all tissues. Data presented as mean ± SEM (n=12 mice/group, p values: **p<0.01, *p<0.05; N.D.: not detected).