Response of brown adipose tissue to an oral glucose load in virgin and lactating rats.

the administration of synthetic oestrogen in the, form of the contraceptive hormone ethynyloestradiol slightly increased the folic acid transported by mechanisms other than solvent drag. Pregnancy, a condition associated with elevated oestrogen concentrations (Shaikh, 1971), did not have a similar effect. Ovariectomy, which in common with the menopause is accompanied by low oestrogen concentrations (Labhsetwar, 1972; Saez et al., 1972), resulted in the greatest decrease in folic acid transfer, it being significant compared with that in male rats. This decrease was valid both'when considering maximal transfer and also when solvent drag of folic acid was accounted for. Furthermore, the decrease in folic acid transfer was corrected towards normal when the replacement-therapyhormone oestradiol was administered to ovariectomized rats. It is apparent from the present study that oestrogen does not affect folic acid transfer to any great extent. However, endocrine systems are complex, and both ovarian hormones and contraceptive steroids may have various subtle indirect effects on both the structure and function of the intestine. In this respect, the minor decreases in folic acid transfer observed in this strictly physiological study could over a prolonged period of time contribute to the development of folate deficiency. We thank Professor J. A. Blair and Dr. C. J. Bailey for their interest in this study.