In vitro binding of steroid hormones by natural and purified fibers

The in vitro binding of estrone, estradiol-17β, estriol, testosterone, dihydrotestosterone, and estrone-3-glucuronide by wheat, oat and corn brans, oat hulls, cellulose, lignin, and cholestyramine resin was measured. Steroid binding was carried out by mixing 50 mg of binding substance with varying substrate quantities (0.037 μCi; 0.50-2.51 pmol/incubation) of 3H-estrone, 3H-estradiol-17β, 3H-estriol, 3H-estrone-3-glucuronide, 4H-testosterone, and 370C for 1 hr with shaking. Following centrifugation of the reaction mixture, a 1 ml aliquot was analyzed for radioactivity. The extent of steroid sequestration was characteristic and reproducible for each hormone. Cholestyramine bound an average of 90% of all the steroids tested, whereas cellulose bound the least (12%). Of the other substances tested, lignin bound 87%; wheat and oat grans, 45% each; corn bran, 44%; and oat hulls, 32% of the unconjugated hormones. The conjugated steroid was less likely to bind than the unconjugated steroids. Lignin appeared to be an important component in the interaction with steroid hormones. The results support the hydrophobic of nature of adsorption and suggest that the components of the fiber in diet should be considered separately when evaluating in vivo metabolic effects. Implications include the possible modification of hormone-dependent cancer risk through dietary intervention