Alterations in polyunsaturated fatty acid composition of cardiac membrane phospholipids and alpha 1 adrenoceptor mediated phosphatidylinositol turnover.
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.
Meij
J T
JT
Department of Biochemistry I, Medical Faculty, Erasmus University Rotterdam, The Netherlands.
Bordoni
A
A
Dekkers
D H
DH
Guarnieri
C
C
Lamers
J M
JM
D000818:Animals; D002478:Cells, Cultured; D015118:Eicosapentaenoic Acid / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D006321:Heart / Q000187:drug effects; D008041:Linoleic Acids / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*
D005230:Fatty Acids, Nonesterified; D005231:Fatty Acids, Unsaturated; D008041:Linoleic Acids; D010716:Phosphatidylinositols; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D015118:Eicosapentaenoic Acid