THE BENEFICIAL EFFECTS OF YEAST ON THE BODY AND GONADAL WEIGHT OF IMMATURE RATS FED ALPHA-ESTRADIOL

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Abstract
Male and [female] rats were placed at weaning on purified rations containing 0.0, 0.2, 1.0 and 5.0 mg. of a-estradiol per kg. of diet. Three basal rations were employed. In two of the rations B vits. were administered as synthetic factors; in the 3d they were present as yeast. Rate of growth was significantly reduced in rats maintained on synthetic rations containing 5 mg. of a-estradiol/kg. of diet. Substitution of yeast for the synthetic vits. in the above rations resulted in a significant increase in body wt. No adverse effects on body wt. were noted at lower levels of [alpha]-estradiol. A significant reduction in gonadal wt. was observed in rats maintained on synthetic rations containing 5 mg. of a -estradiol/kg. of diet, ovaries remaining infantile both in wt. and microscopic appearance and testes revealing a profound depletion of germinal epithelium. Substitution of yeast for the synthetic vits. resulted in a significant increase in gonadal wt. and the maintenance of normal histologic structure. No adverse effects on gonadal wt. or appearance were noted at lower levels of a-estradiol. The suggestion is made that some factor in yeast other than the vits. present in the synthetic rations may be reponsible for the above effects.