text: The effects of orally administered linoleic acid and its autoxidation products on intestinal mucosa in rat.
  Linoleic acid and its autoxidation products, hydroperoxides and their secondary products, were orally administered to rats (350 mg each/rat). Hemorrhage was seen in the alimentary canal at 6 h after the dose of hydroperoxides. To examine their toxicities on intestinal mucosa, the activities of mucous enzymes (sucrase, maltase, and alkaline phosphatase) were measured. Hydroperoxides and their secondary products decreased the enzyme activities in jejunum at 6 h after the doses and increased them in both jejunum and ileum at 15 h, as compared to linoleic acid or saline solution. The decrease of enzyme activity was marked in the hydroperoxide group and the increase was marked in the secondary product group. Then, in in vitro experiments, the effects of autoxidation products on these enzymes were determined. Autoxidation products inactivated only alkaline phosphatase. Thus, the results in vivo disagreed with those in vitro. It was assumed that autoxidation products orally administered attacked a membrane of intestinal microvilli whereas in vitro they directly affected the enzymes.