An unidentified factor in liver required for reproduction in rats
BY B. P. WIESNER AND JOHN YUDKIN
Department of Nutrition, Queen Elizabeth College, University of London
(Received 27 June 1957 — Revised 3 0 October 1957)
It has been known for some time that reproduction in rats is impaired when they are fed on purified diets, and may to some extent be restored by supplements of natural foods such as liver (see, for example, Mapson, 1932; Folley, Henry & Kon, 1947). This earlier work was carried out before the recognition of vitamin BB12 as an essential nutrient.
We too have reported on the effect on reproduction in rats of purified diets containing all the known nutritional factors except vitamin B12 and folic acid (Wiesner & Yudkin, 1951). On this diet, female rats of our albino strain K.C. I took longer to conceive, gained less weight during pregnancy and produced smaller litters than female rats reared on a non-purified stock diet. The most outstanding effect was the complete extinction of true fertility, since all the young born died in an emaciated condition within a few days of birth. T h e supplementation of the purified diet with fresh or dried liver improved reproductive performance and resulted in the survival of more than one-third of the litters. T h e non-viability of the pups, which is the central characteristic of the deficiency induced by the purified diets, was not repaired to the same extent by vitamin B12 as by liver (Wiesner & Yudkin, 1952). We therefore concluded tentatively that liver contains a factor necessary for normal reproduction, which we have called Factor R. I t must not be presumed, of course, that liver is unique in aiding the successful rearing of young by rats given our purified diet. Comprehensive tests for its presence in other foodstuffs have not yet been carried out.
The first part of this communication describes an experiment designed to test that conclusion more decisively by supplementing the purified diets with folic acid and larger doses of vitamin B12 . We were not concerned with the relative fertility of animals on purified and on stock diets, but with a comparison between the preventive effects of liver or of a liver preparation, and of vitamin B12 . The second part is concerned with the effect of the purified diets on reproduction in a different strain of rats.