EFFECT OF DIETARY PHYTOSTEROLS ON CELL-PROLIFERATION AND PROTEIN-KINASE-C ACTIVITY IN RAT COLONIC MUCOSA

The present study investigated the role of phytosterols in colonic cel l proliferation and examined the possible role of protein kinase C (PK C) in this process. A total of 18 male Sprague-Dawley rats weighing 24 0-270 g were fed, for a period of 22 days, one of three experimental d iets: a control diet, a diet supplemented with 0.2% cholic acid, or a diet supplemented with 0.2% cholic acid + 2% dietary phytosterols. Two hours before decapitation, animals were injected with 5'-bromo-2'-deo xyuridine (BrdU, 50 mg/kg body wt ip). Cell proliferation in the proxi mal colon was measured using a monoclonal antibody to BrdU. PKC activi ty in the proximal colonic mucosa was assayed using a myelin basic pro tein as a substrate. Cell proliferation was significantly increased by 276% with 0.2% cholic acid feeding compared with controls. The presen ce of 2% phytosterols in the diet abolished the cholic acid-induced hy perplasia. Cholic acid induced a 31% expansion of the proliferative zo ne. Only the cytosolic PKC was significantly lower in the phytosterol- fed group. Neither the total PKC nor the particulate PKC demonstrated an effect of phytosterols on enzyme activity. fn conclusion, we found that dietary supplementation with 2% phytosterol has a significant pro tective effect on enhanced cell proliferation and that this effect is not mediated through the PKC system.