Studies on Growth. Growth Factors in Liver.

Abstract

Recent investigations have emphasized the value of liver as a dietary supplement in diets apparently adequate with respect to vitamins A and D. No definite information is available, however, concerning the nature of the water soluble substances also present in liver. 1 This is a preliminary report of a study of the nutritional factors concerned with the growth of young white rats, and particularly of the presence of such growth factors in liver.

Young male and female rats, 4 to 5 weeks of age, were used. The basal diet was the fat-free diet of Evans and Burr 2 (purified casein, 25; commercial sucrose, 75; Osborne and Mendel salt mixture, 4). In every case this diet was supplemented daily with 9 drops of cod liver oil. The rats were kept in individual raised cages.

Rats placed upon this basal diet failed to survive. The addition of 0.15 gm. of dried yeast permitted survival but not growth. Growth occurred with the further addition of autoclaved liver or yeast. Rats fed the basal diet plus 0.5 gm. of dried liver daily grew well for 20 to 30 days only. When this diet was supplemented with an extract containing vitamin B₁, prepared by the method of Seidell, 3 growth was resumed. Similar results were obtained using auto-claved liver. These experiments demonstrated that the limiting factor in liver was vitamin B₁ and that the liver was rich in vitamin B₂.

The purified diet supplemented with liver or yeast was lacking in some essential growth factor. Female rats on the mixed stock diet averaged 179 gm. in weight when 120 days of age and were still increasing in weight (Table I). Female rats on the purified diet reached an average maximum weight of 150 to 160 gm. after 90 days (when 120 days of age).