INHIBITION OF ARACHIDONATE RELEASE BY SECRETAGOGUE-STIMULATED PANCREATIC-ISLETS SUPPRESSES BOTH INSULIN-SECRETION AND THE RISE IN BETA-CELL CYTOSOLIC CALCIUM-ION CONCENTRATION
INHIBITION OF ARACHIDONATE RELEASE BY SECRETAGOGUE-STIMULATED PANCREATIC-ISLETS SUPPRESSES BOTH INSULIN-SECRETION AND THE RISE IN BETA-CELL CYTOSOLIC CALCIUM-ION CONCENTRATION
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DOI：
10.1021/bi00052a042
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发表时间：
1993-01-12
期刊：
影响因子：
2.9
通讯作者：
TURK, J
中科院分区：
文献类型：
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作者：
RAMANADHAM, S;GROSS, RW;TURK, J
燃料促分泌剂可诱导胰岛细胞磷脂中酯化花生四烯酸的水解和非酯化花生四烯酸的积累，浓度可达35微米。外源性花生四烯酸(5-30微米)可增强去极化诱导的胰岛胰岛素分泌。在无钙介质中，燃料促分泌剂诱导胰岛磷脂中花生四烯酸的水解发生，提示可能参与了一种不依赖于钙的磷脂酶。在配套文件[Gross et al.，我们证明了主要的胰岛磷脂酶A2是不依赖于钙离子的，受三磷酸腺苷的刺激，并被卤代烯醇内酯自杀底物(E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one.抑制。在这里，我们证明HELSS抑制了D-葡萄糖和M受体激动剂卡巴胆碱刺激的胰岛释放花生四烯酸代谢产物前列腺素E2和胰岛素分泌。前列腺素E_2的释放和胰岛素的分泌均受到抑制，其浓度分布和时间进程相似。HELSS对胰岛[C-14]-葡萄糖氧化为[C-14]CO2，胰岛乳酸脱氢酶、丙氨酸和天冬氨酸氨基转移酶活性，以及氨基甲胆碱诱导的肌醇磷酸蓄积均无影响。用40 mM KCl去极化分离的胰岛β细胞，可引起胞浆[Ca~(2+)]升高，而HELSS对此无影响。相反，HELSS以浓度依赖的方式抑制17 mM D-葡萄糖诱导的β细胞[Ca~(2+)]升高，而外源性花生四烯酸(15微米)对此无明显影响。这些结果表明，燃料促分泌剂激活胰岛非钙依赖的磷脂酶A2，导致非酯化的花生四烯酸释放，从而促进钙离子进入胰岛β细胞，促进胰岛素的分泌。
Fuel secretagogues induce hydrolysis of esterified arachidonic acid from pancreatic islet cell phospholipids and accumulation of nonesterified arachidonate at concentrations up to 35 muM. Exogenous arachidonate (5-30 muM) amplifies depolarization-induced insulin secretion from islets. Fuel secretagogue-induced hydrolysis of arachidonate from islet phospholipids occurs in Ca2+-free medium, suggesting the possible involvement of a Ca2+-independent phospholipase. In the companion paper [Gross et al. (1993) Biochemistry (preceding paper in this issue)], we demonstrated that the major islet phospholipase A2 is Ca2+-independent, ATP-stimulated, and inhibited by the haloenol lactone suicide substrate (HELSS) (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one. Here we demonstrate that HELSS suppressed both release of the arachidonate metabolite prostaglandin E2 and insulin secretion from islets stimulated with D-glucose and the muscarinic agonist carbachol. Both prostaglandin E2 release and insulin secretion were suppressed with similar concentration profiles and time courses. Islet oxidation of [C-14]-glucose to [C-14] CO2, activities of islet lactate dehydrogenase and alanine and aspartate aminotransferases, and carbachol-induced inositol phosphate accumulation in islets were all unaffected by HELSS. Depolarization of isolated beta-cells with 40 mM KCl induced a rise in cytosolic [Ca2+] that was also unaffected by HELSS. In contrast, the 17 mM D-glucose-induced rise in beta-cell [Ca2+] was inhibited by HELSS in a concentration-dependent manner, but that induced by exogenous arachidonate (15 muM) was not. These results suggest that fuel secretagogues activate the islet Ca2+-independent phospholipase A2, resulting in release of nonesterified arachidonate, which facilitates Ca2+ entry into beta-cells and promotes insulin secretion.