Serum estrogen concentration of rats fed soy protein diet and subjected to 20% energy restriction
Forty-eight 4-week-old female Sprague-Dawley rats were fed one of the four experimental diets for four weeks. Groups C-AL and SPI -AL were fed casein or soy protein isolate diets, respectively, ad libitum. The 20% energy restricted groups, C-R and SPI-R were fed casein or soy protein isolate diets at 80% energy intake of C-AL and SPIAL, respectively. Serum estradiol concentration of these rats was determined at the end of feeding period and no significant differences were detected among the four groups. However, the 20% energy restricted groups had 77%-88% of serum estradiol concentration of their ad libitum counterparts . In the second study, 81 sera from 26-week-old rats that had the same four dietary treatments and received either 7, 1 2-Dimethylbe nz(a)anthracene (DMBA) or sesame o il at the age o f 8 weeks were analyzed for estradiol concentration. No signific ant differences in serum estradiol concentrations were detected among the groups . DMBA- treated groups had serum e stradiol con c entration o f 79% - 94% of their sesame oil-treated counterparts. Except for the rats in the sesame oil-treated group which were fed casein ad libitum, all ad libitum groups had higher serum estradiol concentration than their respective restricted groups. The type of the dietary protein did not influence the serum estradiol concentration in these rats.