EFFECT OF DIETARY UNDEGRADED CARRAGEENAN ON COLON CARCINOGENESIS IN F344 RATS TREATED WITH AZOXYMETHANE OR METHYLNITROSOUREA

Abstract

The effect of dietary undegraded carrageenan (Viscarin 402) on colon carcinogenesis was studied in female inbred F344 rats. Weanling rats were fed semipurified diets containing 0 or 15% undegraded carrageenan. At 7 wk of age all animals except controls were given azoxymethane (AOM) s.c. at a dose rate of 8 mg/kg body wt per wk for 10 wk or methylnitrosourea (MNU) intrarectally at a dose level of 2 mg/rat twice a wk and the MNU groups 30 wk after the 1st injection. No tumors were induced in the colon or in other organs of untreated rats fed the control diet. One untreated rat fed the carrageenan diet showed a colon adenoma. The animals fed the carrageenan diet and treated with AOM or MNU had a higher incidence of colorectal tumors (number of rats with colorectal tumors and number of tumors per tumor-bearing rat) than did those fed the control diet and treated similarly. The undegraded carrageenan (Viscarin 402) in the diet had an enhancing effect in colorectal carcinogenesis in rats evoked by AOM or MNU.