Metz S A
J Pharmacol Exp Ther. 1986 Sep;238(3):809-18.
Activation of an islet phospholipase A2 may contribute to glucose-induced insulin release. In order to simulate the accumulation of the resultant hydrolytic products (arachidonic acid, AA; its lipoxygenase-derived oxygenation product 12-hydroxyeicosatetraenoic acid; and lysophospholipids) without many of the other concomitants of beta cell activation, we studied the effects on intact rat islets of p-hydroxymercuribenzoic acid (PHMB), which inhibits the reacylation of lysophospholipids with AA in other cell types. PHMB inhibited in a dose-responsive fashion (-90% at 500 microM) the incorporation of [3H]AA into a "basal" pool or pools whose release and reuptake mechanisms appeared to be largely energy- and Ca++-independent (resistant to inhibition by mannoheptulose, antimycin A or CoCl2); reciprocally, islets prelabeled with [3H]AA accumulated an increased amount of [3H]-12-hydroxyeicosatetraenoic acid (twice basal at 200 microM PHMB and three times basal at 500 microM) when reacylation of any [3H]AA released basally at 1.7 mM glucose was inhibited. PHMB also blocked (by up to 99% at 500 microM) the incorporation of [3H]AA into a functionally defined, glucose-stimulated compartment of fatty acid (tightly coupled to the islet 12-lipoxygenase) whose release and reuptake required metabolic energy and Ca++. It was also demonstrated that PHMB inhibited the esterification of [3H]AA (at low or high glucose concentrations) into specific phospholipids in islet membranes. In parallel with these alterations in lipid metabolism, PHMB caused rapid, potent and reversible increments in insulin release with a threshold concentration (about 25 microM) identical to that inhibiting AA fluxes. PHMB both initiated release (at 1.7 mM glucose) and potentiated the effects of islet fuels (16.7 mM glucose or 15 mM alpha-ketoisocaproic acid). Thus, pharmacologic manipulation of the AA reuptake mechanism is a new approach to unmask potential roles in insulin release of phospholipid hydrolysis products from different lipid pools and in the absence or presence of phospholipase A2 activation.
胰岛磷脂酶A2的激活可能有助于葡萄糖诱导的胰岛素释放。为了模拟水解产物（花生四烯酸，AA；其脂氧合酶衍生的氧化产物12-羟基二十碳四烯酸；以及溶血磷脂）的积累，同时避免β细胞激活带来的许多其他伴随情况，我们研究了对羟基汞苯甲酸（PHMB）对完整大鼠胰岛的影响，PHMB可抑制其他细胞类型中溶血磷脂与AA的再酰化反应。PHMB以剂量依赖的方式抑制（在500μM时抑制率为-90%）[3H]AA掺入一个“基础”池或多个池，其释放和再摄取机制似乎在很大程度上不依赖能量和Ca++（对甘露庚酮糖、抗霉素A或CoCl2的抑制有抗性）；相反，预先用[3H]AA标记的胰岛在1.7 mM葡萄糖时基础释放的任何[3H]AA的再酰化被抑制时，积累了增加量的[3H]-12-羟基二十碳四烯酸（在200μM PHMB时是基础值的两倍，在500μM时是基础值的三倍）。PHMB还阻断了（在500μM时高达99%）[3H]AA掺入一个功能定义的、葡萄糖刺激的脂肪酸区室（与胰岛12-脂氧合酶紧密偶联），其释放和再摄取需要代谢能量和Ca++。还证明PHMB抑制了（在低或高葡萄糖浓度下）[3H]AA酯化为胰岛膜中的特定磷脂。与这些脂质代谢变化同时发生的是，PHMB导致胰岛素释放迅速、有力且可逆地增加，其阈值浓度（约25μM）与抑制AA通量的浓度相同。PHMB既启动了释放（在1.7 mM葡萄糖时），又增强了胰岛燃料（16.7 mM葡萄糖或15 mMα-酮异己酸）的作用。因此，对AA再摄取机制的药理学操作是一种新方法，可揭示来自不同脂质池的磷脂水解产物在胰岛素释放中的潜在作用，无论是否存在磷脂酶A2激活。
