Meij J T, Bordoni A, Dekkers D H, Guarnieri C, Lamers J M
Department of Biochemistry I, Medical Faculty, Erasmus University Rotterdam, The Netherlands.
Cardiovasc Res. 1990 Feb;24(2):94-101. doi: 10.1093/cvr/24.2.94.
STUDY OBJECTIVE - The aim of the study was to investigate the steps at which polyunsaturated fatty acids are involved in alpha 1 adrenoceptor mediated phosphatidylinositol turnover. DESIGN - Phosphatidylinositol turnover rates were investigated after preincubating neonatal rat ventricular myocytes with culture media enriched with linoleic acid (18:2n-6) or eicosapentaenoic acid (20:5n-3) to change the polyunsaturated fatty acid composition of their membrane phospholipids. EXPERIMENTAL MATERIAL - Cardiomyocytes were isolated from ventricles of 2-4 d old Wistar rats by trypsinization and were then cultured. Experiments were started 48 h after seeding, when there was a confluent monolayer of beating cardiomyocytes. MEASUREMENTS and RESULTS - In 18:2n-6 treated cells the 18:2n-6 content in the total phospholipid fraction rose from 45 to 68 nmol.mg-1 protein; in 20:5n-6 treated cells the 20:5n-3 content rose from 1.5 to 12.5 nmol.mg-1 protein, and the docosapentaenoic acid (22:5n-3) content rose from 5.1 to 14.7 nmol.mg-1 protein. The major n-3 fatty acid, 22:6n-3 (11.4 nmol.mg-1 protein), did not change after 20:5n-3 treatment. Although the phosphatidylinositol fraction showed changes paralleling those in the total phospholipids, none were significant. In this fraction the major n-3 fatty acid appeared to be 22:5n-3 (0.4 nmol.mg-1 protein). The fatty acid treated cells were prelabelled with [3H]-inositol to estimate the rate of phosphatidylinositol-4,5-bisphosphate turnover. There were no differences in the rate of [3H]-inositolphosphate formation between control, 18:2n-6 treated cells, and 20:5n-3 treated cells. Prolonged alpha 1 adrenergic stimulation of control and treated cells did not change the polyunsaturated fatty acid composition of the total phospholipid and phosphatidylinositol fractions. CONCLUSIONS - The alpha 1 adrenoceptor mediated phosphatidylinositol turnover rate is not affected by changes in polyunsaturated fatty acid composition of membrane phospholipids, neither does prolonged alpha 1 adrenergic stimulation lead to significant depletion of any specific or total polyunsaturated fatty acids in the phosphatidylinositol lipids.
研究目的——本研究旨在探究多不饱和脂肪酸参与α1肾上腺素能受体介导的磷脂酰肌醇代谢的步骤。
设计——用富含亚油酸（18:2n-6）或二十碳五烯酸（20:5n-3）的培养基预孵育新生大鼠心室肌细胞，以改变其膜磷脂的多不饱和脂肪酸组成，之后研究磷脂酰肌醇的代谢率。
实验材料——通过胰蛋白酶消化从2至4日龄Wistar大鼠的心室中分离出心肌细胞，然后进行培养。接种后48小时开始实验，此时心肌细胞已形成融合的搏动单层。
测量与结果——在经18:2n-6处理的细胞中，总磷脂组分中的18:2n-6含量从45 nmol·mg-1蛋白质升至68 nmol·mg-1蛋白质；在经20:5n-3处理的细胞中，20:5n-3含量从1.5 nmol·mg-1蛋白质升至12.5 nmol·mg-1蛋白质，二十二碳五烯酸（22:5n-3）含量从5.1 nmol·mg-1蛋白质升至14.7 nmol·mg-1蛋白质。主要的n-3脂肪酸22:6n-3（11.4 nmol·mg-1蛋白质）在20:5n-3处理后未发生变化。尽管磷脂酰肌醇组分的变化与总磷脂的变化平行，但均无显著差异。在该组分中，主要的n-3脂肪酸似乎是22:5n-3（0.4 nmol·mg-1蛋白质）。用[3H]-肌醇对脂肪酸处理的细胞进行预标记，以评估磷脂酰肌醇-4,5-二磷酸的代谢率。对照细胞、经18:2n-6处理的细胞和经20:5n-3处理的细胞在[3H]-肌醇磷酸形成速率上没有差异。对对照细胞和处理后的细胞进行长时间的α1肾上腺素能刺激，并未改变总磷脂和磷脂酰肌醇组分的多不饱和脂肪酸组成。
结论——α1肾上腺素能受体介导的磷脂酰肌醇代谢率不受膜磷脂多不饱和脂肪酸组成变化的影响，长时间的α1肾上腺素能刺激也不会导致磷脂酰肌醇脂质中任何特定或总多不饱和脂肪酸的显著消耗。
