Law P Y, Nicksic T D, O'Rourke M A, Koehler J E, Herz A, Loh H H
Mol Pharmacol. 1982 Mar;21(2):492-502.
The effect of cerebroside sulfate, phosphatidylserine, and other phospholipids on opiate receptor function in neuroblastoma N18TG2 cells was studied by incorporation of lipids into the membrane bilayer of viable cells. A concentration- and time-dependent incorporation of sulfatide by N18TG2 cells was observed. The incorporated lipid was not metabolized during the incubation period of up to 48 hr at 37 degrees. Optimal conditions for lipid incorporation were determined to be 4 days after the cell seeding and in 1% fetal calf serum. The incorporated lipid was established to be associated with the plasma membrane fraction of the crude cell homogenate. Furthermore, increases in Vmax but not Km values of the adenylate cyclase for Mg2+, ATP, and prostaglandin E1 were observed in neuroblastoma N18TG2 cells exposed to cerebroside sulfate for 4--6 hr. The incorporation of cerebroside sulfate or phosphatidylserine by N18TG2 cells did not increase the number of opiate binding sites in this cell line as determined by [3H]naloxone, [3H]etorphine, or 3H-labeled D-Ala2-Met5-enkephalinamide binding. Although there was an increase in the affinity of [3H]naloxone binding, linear correlation between the amount of cerebroside sulfate incorporated and the quantity of binding increase was not observed. However, augmentation of both the potencies and the efficacies (maximal inhibitory level) of morphine and enkephalin to regulate adenylate cyclase activity was observed after sulfatide incorporation. At the maximal concentration of cerebroside sulfate used (67 microM) the opiate receptor activity in N18TG2 cells approached that of NG108-15 cells. Identical treatment of N18TG2 cells with cerebroside or psychosine sulfate did not produce any potentiation of the opiate inhibition of adenylate cyclase. Of all of the phospholipids tested--phosphatidylserine, phosphatidylinositol, and phosphatidylcholine--only phosphatidylcholine produced a potentiation of the opiate effect. Both synthetic dipalmitoyl phosphatidylcholine or brain phosphatidylcholine could elicit the potentiation.
通过将脂质掺入活细胞的膜双层中，研究了硫酸脑苷脂、磷脂酰丝氨酸和其他磷脂对神经母细胞瘤N18TG2细胞中阿片受体功能的影响。观察到N18TG2细胞对硫脂的掺入呈浓度和时间依赖性。在37℃下长达48小时的孵育期内，掺入的脂质未发生代谢。确定脂质掺入的最佳条件为细胞接种后4天且在1%胎牛血清中。已确定掺入的脂质与粗细胞匀浆的质膜部分相关。此外，在暴露于硫酸脑苷脂4 - 6小时的神经母细胞瘤N18TG2细胞中，观察到腺苷酸环化酶对Mg2 +、ATP和前列腺素E1的Vmax增加，但Km值未增加。通过[3H]纳洛酮、[3H]埃托啡或3H标记的D - Ala2 - Met5 - 脑啡肽酰胺结合测定，N18TG2细胞掺入硫酸脑苷脂或磷脂酰丝氨酸并未增加该细胞系中阿片结合位点的数量。尽管[3H]纳洛酮结合的亲和力有所增加，但未观察到掺入的硫酸脑苷脂量与结合增加量之间的线性相关性。然而，在掺入硫脂后，观察到吗啡和脑啡肽调节腺苷酸环化酶活性的效力和效能（最大抑制水平）均增强。在所用硫酸脑苷脂的最大浓度（67μM）下，N18TG2细胞中的阿片受体活性接近NG108 - 15细胞。用硫酸脑苷脂或鞘氨醇对N18TG2细胞进行相同处理，未产生阿片对腺苷酸环化酶抑制的任何增强作用。在所有测试的磷脂——磷脂酰丝氨酸、磷脂酰肌醇和磷脂酰胆碱中，只有磷脂酰胆碱产生了阿片效应的增强作用。合成的二棕榈酰磷脂酰胆碱或脑磷脂酰胆碱均可引发这种增强作用。
