Grange E, Deutsch J, Smith Q R, Chang M, Rapoport S I, Purdon A D
Laboratory of Neurosciences, National Institute on Aging, NIH 20892-1582, USA.
J Neurochem. 1995 Nov;65(5):2290-8. doi: 10.1046/j.1471-4159.1995.65052290.x.
In vivo rates of palmitate incorporation into brain phospholipids were measured in awake rats following programmed intravenous infusion of unesterified [9,10-3H]palmitate to maintain constant plasma specific activity. Animals were killed after 2-10 min of infusion by microwave irradiation and analyzed for tracer distribution in brain phospholipid and phospholipid precursor, i.e., brain unesterified palmitate and palmitoyl-CoA, pools. [9,10-3H]Palmitate incorporation into brain phospholipids was linear with time and rapid, with > 50% of brain tracer in choline-containing glycerophospholipids at 2 min of infusion. However, tracer specific activity in brain phospholipid precursor pools was low and averaged only 1.6-1.8% of plasma unesterified palmitate specific activity. Correction for brain palmitoyl-CoA specific activity increased the calculated rate of palmitate incorporation into brain phospholipids (0.52 nmol/s/g) by approximately 60-fold. The results suggest that palmitate incorporation and turnover in brain phospholipids are far more rapid than generally assumed and that this rapid turnover dilutes tracer specific activity in brain palmitoyl-CoA pool owing to release and recycling of unlabeled fatty acid from phospholipid breakdown.
在清醒大鼠中，通过程序化静脉输注未酯化的[9,10-³H]棕榈酸以维持血浆比活性恒定，测定了棕榈酸掺入脑磷脂的体内速率。输注2 - 10分钟后，通过微波辐照处死动物，并分析脑磷脂和磷脂前体（即脑未酯化棕榈酸和棕榈酰辅酶A池）中的示踪剂分布。[9,10-³H]棕榈酸掺入脑磷脂的过程随时间呈线性且迅速，输注2分钟时，超过50%的脑示踪剂存在于含胆碱的甘油磷脂中。然而，脑磷脂前体池中的示踪剂比活性较低，平均仅为血浆未酯化棕榈酸比活性的1.6 - 1.8%。校正脑棕榈酰辅酶A比活性后，计算出的棕榈酸掺入脑磷脂的速率（0.52 nmol/s/g）增加了约60倍。结果表明，棕榈酸掺入和在脑磷脂中的周转比一般认为的要快得多，并且这种快速周转由于磷脂分解产生的未标记脂肪酸的释放和再循环而稀释了脑棕榈酰辅酶A池中的示踪剂比活性。
