SELECTIVE EFFECT OF A DIET-INDUCED DECREASE IN THE ARACHIDONIC-ACID MEMBRANE PHOSPHOLIPID CONTENT ON IN-VITRO PHOSPHOLIPASE-C AND ADENYLATE CYCLASE-MEDIATED PITUITARY-RESPONSE TO ANGIOTENSIN-II
SELECTIVE EFFECT OF A DIET-INDUCED DECREASE IN THE ARACHIDONIC-ACID MEMBRANE PHOSPHOLIPID CONTENT ON IN-VITRO PHOSPHOLIPASE-C AND ADENYLATE CYCLASE-MEDIATED PITUITARY-RESPONSE TO ANGIOTENSIN-II
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DOI：
10.1159/000126774
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发表时间：
1994-10-01
影响因子：
4.1
通讯作者：
KORDON, C
中科院分区：
文献类型：
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作者：
ALESSIO, MLM;LEGER, CL;KORDON, C
幼鼠在断奶后以不含必需脂肪酸(EFA)的饮食喂养6周。摘除脑垂体腺，腺垂体细胞分散并保持在培养中。分别在含有或不含160亩花生四烯酸(AA)的培养液中培养4天后，分析细胞膜脂质，测定基础和刺激激素分泌水平，以获得EFA缺乏或EFA恢复的垂体细胞。在EFA缺乏的细胞膜上，胞膜磷酸甘油酯(PGL)在AA和肾上腺素22：4N-6中被耗尽；在AA存在的情况下孵育克服了这种缺失。枯竭对PGL类有不同程度的影响。AA高度缺乏胆碱磷酸甘油(ChoPG)，仅适度缺乏丝氨酸和乙醇胺磷酸甘油(SerPG和EtnPG)，而完全不缺乏肌醇磷酸甘油，这表明AA在该类别PGL中优先保存。在培养液中添加脂肪酸，对ChoPG和EtnPG完全恢复AA，而对SerPG仅部分恢复AA。随着20：3n-9和22：3n-9的升高，PGL中AA和肾上腺素水平的降低得到了补偿。用放射免疫法测定生长激素和催乳素(PRL)的分泌，用生长激素释放激素、促甲状腺激素释放激素、血管紧张素II(AII)、血管活性肠肽(VIP)或多巴胺刺激细胞，检测膜AA缺陷对激素调节的可能影响。在EFA缺乏的细胞中，无论是基础还是刺激的生长激素分泌都与对照组不同。在EFA缺乏的细胞中，VIP或多巴胺对PRL的调节也不受影响。相反，在缺乏EFA的细胞中，AII，而不是促甲状腺激素释放激素，释放PRL的能力显著降低。在孵育液中添加AA可使其恢复。在EFA缺乏后，AII诱导的肌醇磷酸酶平行抑制和cAMP积累也被观察到。当在膜上测试时，先前观察到的AII对腺苷环化酶的矛盾抑制在缺乏EFA的膜上得到加强。相反，AII的结合不受EFA缺乏的影响。结论是，在我们的实验条件下，EFA缺乏影响AII受体与其效应器的选择性偶联，而不改变结合。这种影响可能涉及到受体与偶联蛋白相互作用的变化。
Young rats were fed on an essential fatty acid (EFA)-deprived diet for 6 weeks after weaning. Their pituitary was removed and adenohypophyseal cells dispersed and maintained in culture. Membrane lipids were analyzed and basal and stimulated levels of hormone secretion were measured after 4-day incubation in a culture medium containing or not 160 mu M arachidonic acid 20:4n-6 (AA) in order to obtain EFA-deficient or EFA-restored pituitary cells, respectively. In EFA-deficient cells membrane phosphoglycerides (PGL) were depleted in AA and adrenic acid 22:4n-6; the deficit was overcome by incubation in the presence of AA. Depletion diversely affected PGL classes. AA was highly depleted in choline phosphoglycerides (ChoPG), only moderately depleted in serine and ethanolamine phosphoglycerides (SerPG and EtnPG) and not depleted at all in inositol phosphoglycerides, suggesting preferential preservation of AA in that class of PGL. Restoration of AA by addition of the fatty acid to the culture medium was complete for ChoPG and EtnPG and only partial for SerPG. Depressed levels of AA and adrenic acid in PGL were compensated for by a concomitant increase in 20:3n-9 and 22:3n-9. Growth hormone and prolactin (PRL) secretion was assessed by radioimmunoassay and possible effects of a membrane AA deficit on hormone regulation were tested in cells challenged by either growth hormone-releasing hormone, thyrotropin-releasing hormone, angiotensin II (AII), vasoactive intestinal peptide (VIP) or dopamine. Neither basal nor stimulated growth hormone secretion was different from controls in EFA-deficient cells. PRL modulation by VIP or dopamine was not affected either in EFA-deficient cells. In contrast, the capacity of AII, but not of thyrotropin-releasing hormone, to release PRL was markedly decreased in EFA-deprived cells. It was restored by addition of AA to the incubation medium. Parallel depression AII-induced inositol phosphates and cAMP accumulation was also observed after EFA deficiency. When tested on membranes, the paradoxical inhibition of adenylate cyclase by AII documented by previous observations was reinforced in EFA-deficient membranes. In contrast, binding of AII was not affected by EFA deficiency. It is concluded that under our experimental conditions EFA deficiency affects selectively coupling of the AII receptor to its effecters without alteration of binding. The effect could involve changes in receptor interactions with coupling proteins.