Phosphatidylcholine Inhibits and Lysophosphatidylcholine Enhances the Lymphatic Absorption of α-Tocopherol in Adult Rats

This study was conducted to compare the effects of enterally infused phosphatidylcholine (PC) and lysophosphatidylcholine (lysoPC) on the lymphatic absorption of α-tocopherol (αTP) in male rats. In expt. 1, bile-diverted rats with mesenteric lymph cannulas were infused at 3.0 mL/h for 8 h with a lipid emulsion containing 5.0 μmol αTP, 565 μmol 14C-triolein (14C-OA) and 396 μmol Na+-taurocholate with 80 μmol 1,2-dipalmitoyl PC (DPPC) or 1,2-dilinoleoyl PC (DLPC) or without PC (NoPC) in 24 mL phosphate-buffered saline (pH 6.6). In expt. 2, the effects of 1,2-dioleoyl PC (DOPC) and 1-oleoyl-2-hydroxy-PC (lysoPC) on αTP and 14C-cholesterol absorption were compared in rats with lymph cannulas. When DPPC or DLPC was infused, the lymphatic absorption of αTP was lowered drastically. The cumulative absorptions of αTP in rats infused with DPPC and DLPC were 45 and 52%, respectively, of the control values (NoPC). No significant difference was noted between the PC groups. In contrast, the absorption of 14C-OA was increased by 42 to 43% in rats infused with DPPC or DLPC compared with that in NoPC rats. Phospholipid outputs also were significantly higher in DPPC (34.0 ± 5.5 μmol/8 h) and DLPC (32.4 ± 2.4 μmol/8 h) rats than in NoPC rats (21.2 ± 4.2 μmol/8 h). When lysoPC was infused, the absorptions of αTP and 14C-cholesterol were increased markedly compared with those for DOPC, with no significant difference in PL output between groups infused with DOPC and lysoPC. These observations provide clear evidence that PC present in a lipid emulsion inhibits αTP absorption, whereas it enhances the absorption of fat. The data also demonstrate that lysoPC simultaneously increases the absorption of αTP and cholesterol. The findings indicate that luminal PC inhibits the absorption of αTP and that hydrolysis of PC is critical to improving the intestinal absorption of the vitamin.