TYPE OF DIETARY FIBER, NOT FAT, ALTERS PHOSPHOLIPASE-D AND ORNITHINE DECARBOXYLASE ACTIVITIES IN THE RAT LARGE-INTESTINE

We investigated the effect of dietary fatty acid composition (n-6 vs. n-3) and fiber (highly fermentable vs. less fermentable) on the activi ties of phospholipase D (PLD) and ornithine decarboxylase (ODC) in the rat large intestine (cecum and proximal and distal colon). Twenty-fou r Sprague Dawley rats (215-270 g) ate synthetic diets with 2% safflowe r oil plus 21.5% safflower or fish oil and 10% cellulose or guar gum f or four weeks. Cecal bile acids and free fatty acids were higher in ra ts fed guar gum than in rats fed cellulose. Rats fed fish oil had more proximal colonic mucosal and cecal bile acids than those fed safflowe r oil. PLD activity was 23% lower in the proximal colon of rats fed gu ar gum than in those fed cellulose, but the mucosal weight was not dif ferent. ODC activity was lower but cecal mucosal wet weight was higher in the cecum of the rats fed guar gum than in the cecum of the rats f ed cellulose. The activities of PLD and ODC are affected by dietary fi ber and may not be accurate markers for tissue growth in the colonic m ucosa.