HIGH AMYLOSE CORN STARCH RETARDED 7,12-DIMETHYLBENZ[A]ANTHRACENE-INDUCED MAMMARY-TUMOR DEVELOPMENT IN FEMALE RATS

The present study was planned to examine the effect of partial replace ment of corn starch (CS) with high amylose corn starch (HAS) on mammar y tumor progression. The first experiment was to evaluate the effects of HAS on 7, 12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumor progression. Two days after DMBA administration (31 mg/kg body weight of rat) at age of 49 days, rats were assigned into 3 groups and fed o ne of the three experimental diets including CS, 30% HAS and 13.6% whe at bran (WB), respectively. The rats were examined weekly for palpable mammary tumors for 112 days. In the middle of experimental period, cu mulative palpable tumors per tumor-bearing rat were significantly lowe r in rats fed the HAS and WE diets than in those fed the CS diet. At a utopsy, both mean tumor number and weight per tumor bearing rat were r educed by 10 similar to 30% in rats fed the HAS and WB diets compared with those in the CS diet, but these differences were not significant. Serum estradiol-17 beta concentration did not differ among rats fed t he CS, HAS and WB diets, although fecal excretion of estradiol-17 beta in rats fed the WE diet was significantly higher than those in rats f ed the CS and HAS diets. In the second experiment, digestibilities of HAS and CS were compared in ileorectostomized rats. The results showed that only 66% of HAS were digested in the small intestine, whereas CS was digested up to 99%. In the 3rd experiment, postprandial blood glu cose concentrations in rats intubated HAS suspension were significantl y depressed when compared with that in rats intubated CS suspension. T hese results suggest that a mild energy restriction in HAS feeding is effective in prevention of mammary tumor progression. (C) 1997 Elsevie r Science Inc.