Blomhoff R, Berg T, Norum K R
Institute for Nutrition Research, School of Medicine, University of Oslo, Norway.
Proc Natl Acad Sci U S A. 1988 May;85(10):3455-8. doi: 10.1073/pnas.85.10.3455.
Newly absorbed chylomicron remnant retinyl ester is endocytosed by parenchymal liver cells, and retinol is subsequently transferred to perisinusoidal stellate cells in liver. In the present study we have used several approaches to elucidate the mechanism for the paracrine transfer of retinol between liver parenchymal and stellate cells. In one series of experiments, chylomicrons labeled with [3H]retinyl palmitate or with retinyl [3H]palmitate were injected intravenously into rats. It was shown that the retinol as well as the palmitate moiety were initially taken up in parenchymal liver cells. However, only the retinol moiety was detected in stellate cells, indicating that the retinyl ester is hydrolyzed before retinol is transferred to stellate cells. It is well known that parenchymal liver cells secrete retinol bound to retinol-binding protein (RBP), and we have recently found that stellate cells do have RBP receptors. Here we report that antibodies against RBP completely block the transfer of retinol from parenchymal to stellate cells. These findings indicate that following uptake of chylomicron remnant retinyl ester in parenchymal cells, the retinyl ester is hydrolyzed, and retinol secreted from parenchymal cells on RBP is taken up by stellate cells by means of RBP receptors.
新吸收的乳糜微粒残粒视黄酯被肝实质细胞内吞，随后视黄醇被转运至肝脏的肝血窦周星状细胞。在本研究中，我们采用了多种方法来阐明肝实质细胞与星状细胞之间视黄醇旁分泌转运的机制。在一系列实验中，将用[3H]棕榈酸视黄酯或[3H]棕榈酸视黄酯标记的乳糜微粒静脉注射到大鼠体内。结果显示，视黄醇以及棕榈酸部分最初被肝实质细胞摄取。然而，仅在星状细胞中检测到视黄醇部分，这表明视黄酯在视黄醇转运至星状细胞之前被水解。众所周知，肝实质细胞分泌与视黄醇结合蛋白（RBP）结合的视黄醇，并且我们最近发现星状细胞确实具有RBP受体。在此我们报告，抗RBP抗体完全阻断视黄醇从实质细胞向星状细胞的转运。这些发现表明，在实质细胞摄取乳糜微粒残粒视黄酯后，视黄酯被水解，由实质细胞分泌的与RBP结合的视黄醇通过RBP受体被星状细胞摄取。
