EFFECT OF GRAPE SEED TANNINS ON THE ACTIVITY OF SOME RAT INTESTINAL ENZYME-ACTIVITIES

The present study was designed to investigate the effects of grape see d tannins on rat intestinal alkaline phosphatase (AP), sucrase and dip eptidyl peptidase IV (DPP IV) activities. An experiment was performed in vivo by dietary supplementation with 2% tannins; this diet was test ed on an experimental group of rats; a control group received a diet w ithout tannins. After 31 days, tannins intake significantly decreased middle-jejunal AP from 123 to 45 mU/mg protein and sucrase activities from 310 to 195 mU/mg protein, while no significant difference appeare d at the duodenal stage (p < 0.05). Ileal DPP IV activity was also sig nificantly reduced (p < 0.05) from 190 to 110 mU/mg protein after tann in intake. Using in vitro experiments on purified brush border membran es, AP activity was found to be inhibited by grape tannins; this inhib ition was prevented by the detergent Triton X-100. The addition of pan creatic-biliary (PB) juice to the incubation medium prevented or rever sed the tannin-inhibited enzyme activity. The present data indicate th at in the duodenal lumen, alkalinity and detergency from the PB secret ion neutralized the ability of tannins to inactivate brush border hydr olase activities and suggest that enzyme inhibition took place once bi le salts were reabsorbed while moving down the gut. This was confirmed by in vitro experiments where sucrase and DPP IV activities inhibited by grape seed tannins were largely recovered after the addition of PB juice to the incubation medium.