Transplacental delivery of retinoid: the role of retinol-binding protein and lipoprotein retinyl ester.
Retinoids are required for normal embryonic development. Both embryonic retinoid deficiency and excess result in congenital malformations. There is little understanding of the physiology underlying retinoid transfer from the maternal circulation to the embryo. We now report studies that explore this process using retinol-binding protein-deficient (RBP-/-) mice and mice that express human RBP on the RBP-/-) background. Our studies establish that dietary retinoid, bound to lipoproteins, can serve as an important source for meeting tissue retinoid requirements during embryogenesis. Indeed, retinyl ester concentrations in the circulations of pregnant RBP-/- mice are significantly elevated over those observed in wild-type mice, suggesting that lipoprotein retinyl esters may compensate for the absence of retinol-RBP during pregnancy. We also demonstrate, contrary to earlier proposals, that maternal RBP does not cross the placenta and cannot enter the fetal circulation. Overall, our data indicate that both retinol-RBP and retinyl esters bound to lipoproteins are able to provide sufficient retinoid to the embryo to allow for normal embryonic development.
Quadro
Loredana
L
Institute of Cancer Research, College of Physicians and Surgeons, Columbia Univ., New York, NY 10032, USA.
Hamberger
Leora
L
Gottesman
Max E
ME
Colantuoni
Vittorio
V
Ramakrishnan
Rajasekhar
R
Blaner
William S
WS
D000704:Analysis of Variance; D000818:Animals; D004622:Embryo, Mammalian / Q000378:metabolism; D005314:Embryonic and Fetal Development / Q000502:physiology; D005260:Female; D008074:Lipoproteins / Q000097:blood / Q000502:physiology*; D008431:Maternal-Fetal Exchange / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011994:Recombinant Proteins; D012176:Retinoids / Q000172:deficiency / Q000378:metabolism*; D012177:Retinol-Binding Proteins / Q000172:deficiency / Q000502:physiology*; D000084562:Retinyl Esters
D008074:Lipoproteins; D011994:Recombinant Proteins; D012176:Retinoids; D012177:Retinol-Binding Proteins; D000084562:Retinyl Esters; C022081:retinyl ester lipoprotein complex