SIMULTANEOUS CHANGES IN LIPID-COMPOSITION, FLUIDITY AND ENZYME-ACTIVITY IN PIGLET INTESTINAL BRUSH-BORDER MEMBRANE AS AFFECTED BY DIETARY POLYUNSATURATED FATTY-ACID DEFICIENCY

The effects of dietary polyunsaturated fatty acid (PUFA) deficiency on intestinal brush border membrane (BBM) fluidity, lipid composition and 5'-nucleotidase activity were examined in piglets. Cholesterol/phospholipid and sphingomyelin (SM)/phosphatidylcholine (PC) ratios were unaffected. However, fluidity was decreased in the external regions and also tended to decrease in the core of the PUFA-deficient pig membrane lipid bilayer. Therefore, the change in the membrane physical properties seemed to be due to the large diet-induced alteration in the phospholipid (PL) fatty acid composition and to the concomitant decrease in PC and increase in phosphatidylserine levels. In the membrane total PL, the arachidonic acid level was slightly lowered, while linoleic, eicosapentaenoic and docosahexaenoic acid levels markedly decreased. PC was mainly concerned by the altered distribution of unsaturated fatty acids, but not SM. However, a significant decrease in (n - 6)/(n - 3) ratio occurred in the latter. These structural changes were associated with a higher 5'-nucleotidase activity in the intestinal BBM of PUFA-deficient as compared to control piglets.