[Cell membrane and phospholipids].

Abstract

After a short review of the structure of phospholipids, the authors describe the organisation of these compounds in the cell membrane and the metabolic pathways responsible for their degradation. The latter involve the phospholipases C and A2. The first enzyme is the key to practically all cellular activation because the specific hydrolysis of phosphatidylinositol--4,5-biphosphate generates two intracellular messengers, diglycerides and inositol--1,4,5-triphosphate which activate, respectively, a specific kinase and mobilise the calcium. This mobilisation of calcium is essential for the activation of the phospholipase A2 which regulates the liberation of arachidonic acid and lysophosphatidylcholine, precursors of different lipid mediators (prostaglandins, thromboxanes, leukotrienes, platelet activating factor or PAF-acether...). The production of these derivatives represents a system of amplification and recruitment outside the cell, explaining the possible involvement of these metabolic pathways in the physiological and pharmacological regulation of the different cells of the cardiovascular system (platelets, endothelial cells, smooth muscle cells...).