Ilincheta de Boschero M G, Giusto N M, Bazán N G
Instituto de Investigaciones Bioquímícas, Universidad Nacional del Sur y Consejo Nacional de Investigaciones Científicas y Técnicas, Bahía Blanca, Argentina.
Neurochem Int. 1980;1C:17-28.
The de novo biosynthesis of phospholipids and glycerides was followed in subcellular fractions from bovine retinas incubated during short periods with radioactive glycerol. The labeling of lipid classes was determined in the following fractions: rod outer segments, P(1), P(2), microsomes and soluble. A highly labeled phosphatidic acid was found in microsomal fractions with a maximum at 5 min relative to other lipids labeling. The labeling of phospholipids and glycerides from microsomes as well as from other fractions was rapid. The soluble contained minor quantities of phospholipids with high radioactivity. Using radioactive glycerol and amphiphilic drugs the rates of phosphatidic acid synthesis in microsomal membranes were assessed. Moreover, in agreement with previous studies from this laboratory showing that phosphatidic acid contains a high proportion of docosahexaenoate, it is demonstrated that this fatty acid is acylated in the biosynthetic route leading to phosphatidic acid formation. Phosphatidylserine is synthesized from radioactive serine and also through a Ca(2+) independent pathway not involving phosphatidylethanolamine. Phosphatidylethanolamine is also formed by serine decarboxylation. Amphiphilic drugs greatly stimulate phosphatidylserine synthesis. Extracellular Ca(2+) stimulates the synthesis of phosphatidylserine and its decarboxylation. Besides, Ca(2+) potentiates the phospholipid effect exerted by propranolol. The synthesis of phosphatidylinositol as well as that of other minor acidic phospholipids seems to operate in a coordinated manner under different experimental conditions. The microsomal system of the retina generates a docosahexaenoyl enriched phosphatidic acid at high rates. In addition to the turnover of different phospholipid moieties there are active pathways for the de novo biosynthesis of membrane lipids in the retina.
用放射性甘油对牛视网膜进行短期孵育，然后跟踪磷脂和甘油酯的从头生物合成过程。在以下亚细胞组分中测定脂质类别的标记情况：视杆细胞外段、P(1)、P(2)、微粒体和可溶性部分。在微粒体组分中发现了一种高度标记的磷脂酸，相对于其他脂质标记，在5分钟时达到最大值。微粒体以及其他组分中磷脂和甘油酯的标记迅速。可溶性部分含有少量具有高放射性的磷脂。使用放射性甘油和两亲性药物评估了微粒体膜中磷脂酸的合成速率。此外，与本实验室先前的研究一致，该研究表明磷脂酸含有高比例的二十二碳六烯酸，结果表明这种脂肪酸在导致磷脂酸形成的生物合成途径中被酰化。磷脂酰丝氨酸由放射性丝氨酸合成，也通过不涉及磷脂酰乙醇胺的不依赖Ca(2+)的途径合成。磷脂酰乙醇胺也通过丝氨酸脱羧形成。两亲性药物极大地刺激磷脂酰丝氨酸的合成。细胞外Ca(2+)刺激磷脂酰丝氨酸的合成及其脱羧。此外，Ca(2+)增强了普萘洛尔对磷脂的作用。磷脂酰肌醇以及其他少量酸性磷脂的合成在不同实验条件下似乎以协调的方式进行。视网膜的微粒体系统能高速生成富含二十二碳六烯酰基的磷脂酸。除了不同磷脂部分的周转外，视网膜中还存在膜脂从头生物合成的活跃途径。
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