Absorption of retinol from the retinol:retinol-binding protein complex by small intestinal gut sheets from the rat.
Absorption of retinol by the absorptive cells of the small intestine is a necessary first step in the metabolism of vitamin A. Previous studies had suggested that absorption of retinol from the retinol:retinol-binding protein complex (retinol:RBP) might be receptor mediated. We investigated the specificity of this process by determining the absorption of retinol from retinol:RBP by small intestinal sheets obtained from the suckling rat. We found that the absorption of retinol from retinol:RBP was a saturable process. Unlike the absorption of free retinol, absorption of retinol from retinol:RBP was not inhibited by N-ethylmaleimide. The absorption was specifically competable by unlabeled retinol:RBP and by both apo- and holocellular retinol-binding protein, but not by beta-lactoglobulin. This suggests that a specific mechanism is present for the absorption of retinol bound to RBP.
Dew
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School of Medicine, Vanderbilt University, Nashville, Tennessee, 37232, USA.
Ong
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D000818:Animals; D001692:Biological Transport; D066298:In Vitro Techniques; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism; D007421:Intestine, Small / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012177:Retinol-Binding Proteins / Q000378:metabolism*; D014801:Vitamin A / Q000378:metabolism*
D012177:Retinol-Binding Proteins; D014801:Vitamin A