METOPROLOL EFFECT ON FATTY ACIDS COMPOSITION OF CELL MEMBRANE PHOSPHOLIPIDS

It is quite well known that β-blockers influence the stability of cell membranes, but the effect of metoprolol on the composition of cell membrane lipids is not established. On the other hand, synchronous culture of Chlorella vulgaris cells, which consists of cells brought to the same developmental stage by cycling lighting, provides a convenient biological model in unidirectional analyses aimed at assessment of effects of xenobiotics on cells. Advantages of the model include short life cycle and possibility to control metabolic processes of the cells across the broad range. We assessed the effect of metoprolol on fatty acids composition of cell membrane phospholipids in consecutive life cycle stages of Chlorella vulgaris. Lipids were extracted using a chlorofonn/methanol method. Phospholipids were precipitated from the chloroform phase with cold acetone and following centrifugation the pellet of phospholipids was hydrolyzed in alkaline solution. Fatty acids were extracted with petroleum ether and then methylated with BF₃-methanol. This protocol produced methyl esters of fatty acids which were subjected to GC-MS analysis. Metoprolol had no effect on the number of progeny cells of Chlorella vulgaris throughout their life cycle at the concentration range tested (5x10^-5 M, 5x10^-6 M, 5x10^-7 M). However, we observed stimulation of biological activity of Chlorclla cells as measured by spectrophotomctry at λ=680 nm. Metoprolol, at the highest concentration, increased phospholipids content in mother cells. Simultaneously, relative amount and saturation level of thc fatty acids remained constant.