Effect of dietary linolenic acid on endotoxin-induced thromboxane and prostacyclin production by equine peritoneal macrophages.

In laboratory animals, the incorporation of alpha linolenic acid or other n-3 series fatty acids into the diet results in marked changes in cell membrane composition as well as arachidonic acid metabolism. The purpose of the present study was to determine whether endotoxin-induced thromboxane A2 (TxA2) and/or prostacyclin (PGI2) production by equine peritoneal macrophages was altered by feeding horses a diet containing 8% linseed oil as a source of alpha linolenic acid for 8 weeks. Peritoneal macrophages were cultured in vitro in the presence of endotoxin (LPS) (0.5-500 ng/ml) or calcium ionophore for 6 and 24 hours. After horses were fed the alpha linolenic acid-enriched diet, their peritoneal macrophage production of TxA2 was reduced in response to 0.5 ng/ml and 5 ng/ml LPS. compared to that before the diet (P less than .05). The production of PGI2 during 6 hour incubation with 5 ng/ml and 50 ng/ml LPS and during 24 hour incubation with 5 ng/ml LPS were reduced, compared to that before the diet (P less than .05). Peritoneal macrophage production of PGI2 during 24 hour incubation with nothing, LPS (0.5 ng/ml, 5 ng/ml and 500 ng/ml), and calcium ionophore was greater than during 6 hour incubation, after horses were fed the ALA-rich diet (P less than .05). Results suggest that linseed oil supplementation may be an aid in prophylaxis of endotoxemia in horses.