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Transport of retinol from the blood to the retina: Involvement of high molecular weight lipoproteins as intracellular carriers

1976; Elsevier BV; Volume: 22; Issue: 5 Linguagem: Inglês

10.1016/0014-4835(76)90178-0

1096-0007

J Heller, Dean Bok,

Antioxidant Activity and Oxidative Stress

Abstract Pigment epithelium and rod outer segments enriched fractions from bovine eyes were found to contain soluble intracellular proteins that bind retinol. The proteins were identified as high molecular weight lipoglycoproteins (at least 1·5 × 10 6 daltons). The cytosol retinol-binding lipoprotein from pigment epithelium contained 28% lipid (by weight) while that from the rod outer segment fractions lipoprotein contained 65% lipid. The lipids in both cases were predominately phosphatidylcholine and cholesterol, while triglycerides were absent. The protein fractions of both binding activities contained several different polypeptide chains varying in size from about 50 000 to 200 000 daltons. The protein part of these complex molecules also contained a carbohydrate moiety. The absorption and circular dichroism spectra of the cytosol retinol-binding protein from pigment epithelial cells and rod outer segment fractions were different. From these experiments we concluded that bovine pigment epithelial cells and rod outer segment fractions contain high molecular weight, soluble lipogylcoproteins that bind retinol. The two lipoglycoproteins differ in diffusion coefficient, composition and optical properties.