Dew S E, Ong D E
School of Medicine, Vanderbilt University, Nashville, Tennessee, 37232, USA.
Arch Biochem Biophys. 1997 Feb 15;338(2):233-6. doi: 10.1006/abbi.1996.9830.
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.
小肠吸收细胞对视黄醇的吸收是维生素A代谢过程中必要的第一步。先前的研究表明，视黄醇：视黄醇结合蛋白复合物（视黄醇：RBP）中视黄醇的吸收可能是受体介导的。我们通过测定从乳鼠获得的小肠片对视黄醇：RBP中视黄醇的吸收来研究这一过程的特异性。我们发现，视黄醇：RBP中视黄醇的吸收是一个可饱和的过程。与游离视黄醇的吸收不同，视黄醇：RBP中视黄醇的吸收不受N-乙基马来酰亚胺的抑制。该吸收可被未标记的视黄醇：RBP以及脱辅基和全细胞视黄醇结合蛋白特异性竞争，但不能被β-乳球蛋白竞争。这表明存在一种特异性机制用于吸收与RBP结合的视黄醇。
