We have previously shown that mice fed the American Institute of Nutrition (AIN-76A) purified diet experience a significant increase in uterine-body weight (U:BW) ratios when compared to the U:BW ratios of mice fed Purina #5002, a closed formula natual ingredient diet. The AIN-76A diet contains 65% carbohydrate with 50% coming from sucrose or dextrose and 15% from corn starch. The objective of this study was to determine whether fat and carbohydrate content contribute to unexpected uterine growth promoting activity observed in mice fed the AIN-76A diet. Bioassays were performed using CD-1 mice weaned at 15 days of age and randomly assigned to #5002 diet fortified with corn starch, sucrose, dextrose, corn oil, or soybean oil at the 10% and/or 25% level and to #5002 diet containing 0, 4, or 6 ppb diethylstilbestrol (DES). Uterine:BW ratios were determined on 15 mice/diet at 5 and 7 days post feeding. The U:BW ratios of mice fed #5002 diet fortified with corn oil, soybean oil, sucrose, dextrose or cornstarch were similar to each other, and were higher than the U:BW ratios of mice fed the standard #5002 diet without added DES. This increase in U:BW ratios is similar to the U:BW ratios of mice fed the #5002 diet containing 4 ppb DES. It was concluded that both the fat and the carbohydrate content of the AIN-76A diet contributed to its uterine growth promoting activity.
