Canthaxanthin saturation of serum lipoproteins from immature rainbow trout (Oncorhynchus mykiss)

Abstract Lipoproteins from immature rainbow trout serum fed a diet containing 100 mg cantaxanthin kg −1 of feed during 8 days were separated by ultracentrifugation. Canthaxanthin in the lipoprotein fraction amounted to 1.2, 1.8, 0.7 μ g of canthaxanthin ml −1 of serum for VLDL, LDL, and HDL, respectively. Canthaxanthin, previously dissolved in ethyl ether, was added slowly (50 μ l ml −1 of lipoprotein at a time) while gently stirring and evaporating the ethyl ether with N 2 . After saturation, the canthaxanthin content in the lipoprotein increased about 100-fold, to 80.6, 152.8, 145.7 μ g of canthaxanthin ml −1 serum for VLDL, LDL and HDL, respectively. It is concluded that the binding capacity of lipoproteins is not a limiting factor for carotenoid transport in trout.