Two-month-old outbred female LIO rats were exposed weekly to 15 (experiment I, groups 1, 2 and 3) or to 5 (experiment II, groups 4, 5 and 6) subcutaneous injections of 1,2-dimethylhydrazine (DMH) at a single dose of 21 mg/kg of body weight. From the day of the first injection of the carcinogen, the rats from groups 2, 3, 5 and 6 were given Aqualen(R) in their diet. In both experiments rats were fed Aqualen five times per week together with lab chow at the daily dose of 0.1 g/kg (groups 2 and 5) or 1.0 g/kg (groups 3 and 6) of body weight, Additionally, other rats were not exposed to the carcinogen and served as an intact control (group 7) or were given Aqualen with the diet at the daily dose of 0.1 g/kg (group 8) or 1.0 g/kg (group 9). These experiments were finalized 6 months after the first injection of DMH. In experiments I and II, the majority of tumors were localized in the descending colon, Tumors of the small intestines developed only in rats from experiment I. The total incidence of colon tumors as well as tumors in different parts of the colon and the mean number of tumors per rat were much higher in rats from all groups in experiment I than in the rats from experiment II. In experiment I supplementation of Aqualen to the diet was followed by a decrease in the incidence of tumors in the ascending colon and by a decrease in the number of tumors per rat in both ascending and descending colons regardless of the dose of the enterosorbent. In experiment IT the effect of Aqualen was stronger than in experiment I - the enterosorbent decreased both the tumor incidence and the multiplicity in the total colon, its ascending and descending parts and in the rectum. In experiments I and II the percentage of small colon tumors among rats exposed to Aqualen (groups 2, 3, 5 and 6) was higher than that of the controls (groups 1 and 4). Most of detected intestinal tumors were classified as adenocarcinomas. The level of tumor differentiation was higher in rats exposed to Aqualen. There were no pathological changes observed in rats exposed to Aqualen without DMH. Carcinogen treatment resulted in an increase of serum glucose and cholesterol levels whereas Aqualen normalized these changes. Thus, our results demonstrate the inhibitory effect of activated carbon fiber adsorbent Aqualen on intestinal carcinogenesis in rats. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.
