Purdon D, Arai T, Rapoport S
Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA.
J Lipid Res. 1997 Mar;38(3):526-30.
Awake adult rats were given a solution of [9,10-3H]palmitate ([3H]PAM) by gavage. The appearance of radiolabel in plasma lipid fractions was monitored by thin-layer chromatography at fixed intervals thereafter. At 2 h, the rats were killed by microwave irradiation and radioactivity in whole brain and individual brain phospholipids was determined. In plasma, esterified [3H]PAM was mainly associated with triglyceride, phospholipid, and cholesterol ester. Radioactivity appeared to a larger extent in triglyceride than in unesterified fatty acid, suggesting that unesterified [3H]PAM in plasma was largely due to release from esterified [3H]PAM by lipoprotein lipase hydrolysis. Brain radioactivity could be accounted for entirely by incorporation of unesterified plasma [3H]PAM. Esterified [3H]PAM in chylomicrons or lipoproteins was calculated to make no measurable contribution using a published value for the incorporation coefficient of [3H]PAM into brain in the evaluation. These results suggest that ingested palmitic acid (PAM) in adult rats enters blood as esterified triglyceride within chylomicrons and lipoproteins and, in part, eventually is converted to circulating unesterified PAM. It is the circulating unesterified PAM that is incorporated into brain from blood, whereas esterified PAM within plasma chlomicrons and lipoproteins makes no measurable direct contribution.
给清醒的成年大鼠经口灌胃给予[9,10-3H]棕榈酸酯([3H]PAM)溶液。此后，通过薄层色谱法在固定时间间隔监测血浆脂质组分中放射性标记物的出现情况。2小时后，通过微波辐射处死大鼠，并测定全脑和各个脑磷脂中的放射性。在血浆中，酯化的[3H]PAM主要与甘油三酯、磷脂和胆固醇酯相关。放射性在甘油三酯中的出现程度大于未酯化脂肪酸，这表明血浆中未酯化的[3H]PAM很大程度上是由于脂蛋白脂肪酶水解酯化的[3H]PAM释放所致。脑放射性完全可以由未酯化的血浆[3H]PAM的掺入来解释。在评估中，使用已发表的[3H]PAM掺入脑的掺入系数值计算得出，乳糜微粒或脂蛋白中的酯化[3H]PAM没有可测量的贡献。这些结果表明，成年大鼠摄入的棕榈酸(PAM)以乳糜微粒和脂蛋白中酯化的甘油三酯形式进入血液，并且部分最终转化为循环中的未酯化PAM。正是循环中的未酯化PAM从血液中掺入脑内，而血浆乳糜微粒和脂蛋白中的酯化PAM没有可测量的直接贡献。
