Dietary fat and phospholipase A2 activity of Sprague-Dawley rat large intestine.

The present studies were conducted to examine the effect of dietary lipid content and composition [(n-6) vs. (n-3) fatty acids] on the activity of mucosal phospholipase (PL)A2 of the large intestinal tract of rats. Three segments of the large intestinal tract were examined: cecum, proximal colon and distal colon. Weanling male Sprague-Dawley rats were fed diets containing either 5% (LS) or 16% safflower (HS) or 14% menhaden oil plus 2% safflower oil (HM) for 3 wk with the oil replacing starch in the HS and HM diets on a weight basis. The lipid extracts of microsomal fractions from mucosal scrapings were examined for phospholipid and cholesterol content and fatty acid composition. Phospholipase A2 was assayed using a fluorescent substrate. Rats fed the high fat diets had lower PLA2 specific activities. The (n-3) or (n-6) fatty acid enrichment of the membranes had no effect of the activity of the enzyme. The activity of the enzyme decreased aborally from the cecum to the distal colon; the proximal colon had an intermediate specific activity.