Said H M, Ong D E, Shingleton J L
Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN.
Am J Clin Nutr. 1989 Apr;49(4):690-4. doi: 10.1093/ajcn/49.4.690.
The effect of bovine milk beta-lactoglobulin (BLG) on intestinal uptake of retinol was examined in suckling rats with the everted sac technique. Uptake of 0.06 mumol retinol/L bound to BLG (BLG-retinol) was significantly (p less than 0.01) higher than that of 0.06 mumol free retinol/L both in the jejunum and the ileum. The enhancing effect of BLG on retinol uptake was specific because equimolar concentrations of bovine serum albumin and lactoferrin had no effect on retinol uptake. However, serum retinol-binding protein (RBP), which shares structural and conformational similarities with BLG, also enhanced retinol uptake. BLG, BLG-retinol, and RBP-retinol all inhibited the uptake of retinol from BLG-[3H]retinol in a concentration-dependent manner. Uptake of retinol from BLG-retinol was saturable (apparent Km = 5.6 mumol/L, Vmax = 22.7 nmol.g-1.5 min-1), not affected by metabolic inhibitors, and partially temperature dependent (Q10 = 2.77). BLG also significantly (p less than 0.01) enhanced retinol uptake in the intestine of adult rats. These results demonstrate that BLG specifically enhances intestinal uptake of retinol and suggest the possibility of a receptor for BLG-like proteins at the brush border membrane of the enterocyte.
采用外翻肠囊技术，在乳鼠中研究了牛乳β-乳球蛋白（BLG）对视黄醇肠道摄取的影响。在空肠和回肠中，与BLG结合的0.06μmol视黄醇/ L（BLG - 视黄醇）的摄取量显著高于（p <0.01）0.06μmol游离视黄醇/ L。BLG对视黄醇摄取的增强作用具有特异性，因为等摩尔浓度的牛血清白蛋白和乳铁蛋白对视黄醇摄取没有影响。然而，与BLG具有结构和构象相似性的血清视黄醇结合蛋白（RBP）也增强了视黄醇的摄取。BLG、BLG - 视黄醇和RBP - 视黄醇均以浓度依赖性方式抑制从BLG - [3H]视黄醇中摄取视黄醇。从BLG - 视黄醇中摄取视黄醇是可饱和的（表观Km = 5.6μmol/L，Vmax = 22.7 nmol·g-1·5 min-1），不受代谢抑制剂影响，且部分依赖温度（Q10 = 2.77）。BLG也显著（p <0.01）增强了成年大鼠肠道中视黄醇的摄取。这些结果表明，BLG特异性增强视黄醇的肠道摄取，并提示在肠细胞刷状缘膜上可能存在BLG样蛋白的受体。
