DIETARY MANIPULATION OF PLASMA CAROTENOID CONCENTRATIONS OF SQUIRREL-MONKEYS (SAIMIRI-SCIUREUS)

Primate retinas accumulate the dihydroxy xanthophylls, lutein and zeax anthin, from the diet via the plasma. Control of plasma concentrations of these carotenoids may be useful for prevention of retinal disease by manipulating carotenoid content of the retina. We have measured the plasma response of male squirrel monkeys to changes in the carotenoid content of a nonpurified diet. We have also supplemented the diet wit h zeaxanthin and beta-carotene. Plasma responses to dietary changes we re rapid. Within one week, most of the change in plasma concentrations had already occurred. Within two weeks of increasing zeaxanthin intak e, plasma zeaxanthin concentrations were at a new, relatively stable l evel. beta-carotene concentrations in the plasma were low while the mo nkeys were consuming a standard laboratory diet, and were only slightl y increased by supplementation. Plasma lutein concentrations were unaf fected by zeaxanthin supplementation. Our results suggest that it shou ld be possible to manipulate plasma concentrations of each of the reti nal carotenoids with little impact on the plasma concentrations of the other. This will facilitate exploration of the rates of accumulation of lutein and zeaxanthin in the retina, as well as exploration of the possibility of bioconversion from one xanthophyll to another.