Kunievsky B, Bazan N G, Yavin E
Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel.
J Neurochem. 1992 Nov;59(5):1812-9. doi: 10.1111/j.1471-4159.1992.tb11014.x.
Intracerebral administration of [3H]arachidonic acid ([3H]ArA) into 19-20-day-old rat embryos, resulted in a rapid incorporation of label into brain lipids. One hour after injection, 55.6 +/- 8.2, 18.0 +/- 3.4, and 13.7 +/- 1.3% of the total radioactivity was associated with phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine, respectively. Approximately 10% of radioactivity was found acylated in neutral lipids of which free ArA comprised only 1.5 +/- 0.2% of the total radioactivity. Complete restriction of the maternal-fetal circulation for < or = 40 min did not affect the rate of [3H]ArA incorporation (t1/2 = 2 min) into fetal brain lipids, suggesting an effective acylation mechanism that proceeds irrespective of the impaired blood flow. After a short restriction period (5 min), the radioactivity in diacylglycerol was elevated by 50%. After a longer restriction period (20 min), the radioactivity in the free fatty acid and diacylglycerol fractions increased to values of 130 and 87%, respectively. Polyphosphoinositides prelabeled with either [3H]ArA or 32P were rapidly degraded after 5 min of ischemia. After 20 min, the decrease in phosphatidylinositol-4-phosphate and phosphatidylinositol-4,5-bisphosphate radioactivity was 47 and 70%, respectively. Double labeling of phospholipids with [14C]palmitic acid and [3H]ArA indicated a preferential loss of [3H]ArA within the polyphosphoinositide species after 20 min, but not after 5 min of ischemia. The specific activity of [14C]palmitate remained unchanged. The current data suggest phospholipase C-mediated diacylglycerol formation at the beginning of the insult followed by a phospholipase A2-mediated ArA liberation at a later time, both enzymes presumably acting preferentially on polyphosphoinositide species.
向19 - 20日龄大鼠胚胎脑内注射[3H]花生四烯酸（[3H]ArA），会使标记物迅速掺入脑脂质中。注射后1小时，总放射性的55.6±8.2%、18.0±3.4%和13.7±1.3%分别与磷脂酰胆碱、磷脂酰肌醇和磷脂酰乙醇胺相关。约10%的放射性在中性脂质中被酰化，其中游离ArA仅占总放射性的1.5±0.2%。母体 - 胎儿循环完全受限≤40分钟并不影响[3H]ArA掺入（t1/2 = 2分钟）到胎儿脑脂质中的速率，这表明存在一种有效的酰化机制，该机制不受血流受损的影响而继续进行。在短暂受限期（5分钟）后，二酰甘油中的放射性升高了50%。在较长受限期（20分钟）后，游离脂肪酸和二酰甘油部分的放射性分别增加到130%和87%的值。用[3H]ArA或32P预标记的多磷酸肌醇在缺血5分钟后迅速降解。20分钟后，磷脂酰肌醇 - 4 - 磷酸和磷脂酰肌醇 - 4,5 - 二磷酸放射性的降低分别为47%和70%。用[14C]棕榈酸和[3H]ArA对磷脂进行双重标记表明，缺血20分钟后，但5分钟时未出现，多磷酸肌醇种类中[3H]ArA优先丢失。[14C]棕榈酸的比活性保持不变。目前的数据表明，在损伤开始时磷脂酶C介导二酰甘油形成，随后在稍后时间磷脂酶A2介导ArA释放，这两种酶可能优先作用于多磷酸肌醇种类。
