ESSENTIAL FATTY-ACID DEFICIENCY IN THE PIG - EFFECTS ON EICOSANOID BASAL LEVELS AND IN-VITRO SYNTHESIS BY THE SMALL-INTESTINE

The influence of nutritional essential fatty acid (FFA) deficiency on arachidonate metabolism by porcine small intestine has been studied. G reat care was exercised in the manipulation of the jejunal wall to avo id artefactual metabolism of arachidonate. Thus, jejunal wall was froz en in liquid nitrogen after organ removal and washing, and subsequentl y lyophilized. This lyophilized tissue was used as starting material f or all experiments, including organic solvent extractions (for basal l evel determinations) and reconstitution in aqueous buffer (for neosynt hesis experiments). Feeding pigs with a low linoleate diet for 12 week s resulted in a 36% diminution in the % of arachidonate in jejunal pho spholipids. nasal levels of 6-keto prostaglandin F-1 alpha (6-keto PGF (1 alpha)), thromboxane B-2 (TXB(2)), PGF(2 alpha), PGE(2), PGD(2) and leukotriene B-4 (LTB(4)) mere not altered in the EFA-deficient state. However, we observed a significant lowering of the synthesis of each of these eicosanoids (except LTB(4)) by the EFA-deficient jejunum duri ng brief (15s) in vitro neosynthesis experiments. The origin of arachi donate as a substrate of PG endoperoxide synthase, also named PGH synt hase or cyclooxygenase (Cox) in these neosynthesis experiments is prob ably a non-esterified fatty acid pool since, (1) neosynthesis was not inhibited by the phospholipase A(2) (PLA(2)) inhibitor parabromophenac ylbromide, and (2) substantial amounts of arachidonic acid were found in the jejunum, frozen or lyophilized. Cox activity of the lyophilized jejunum and Cox content of liver and intestine microsomes were not mo dified in the EFA-deficient state. A [1-C-14] arachidonic acid metabol ic profile of the porcine jejunal mucosa was established: PGE(2) and P GF(2 alpha) were the major PGs synthesized, together with another meta bolite which was identified as 12-hydroxyeicosatetraenoic acid (12-HET E) due to its chromatographic retention time.