Some Observations on the Role of Folic Acid in Utilization of Homocystine by the Rat

Abstract

Rats on a basal diet with homocystine as the sole source of sulfur-containing amino acids, and with no dietary source of labile methyl donors will grow. Addition of sulfasuxidine to the diet will kill the intestinal flora and cause cessation of growth. This indicates that the flora under these conditions produce factors necessary for growth. Sulfasuxidine-fed rats on basal diet will grow if Liver Extract Lilly is added to diet,indicating that substances contained in this extract are necessary for growth. Four rats placed for 12 days on basal diet + 62.5 mg. of ryzamin-B unfortified (Wellcome Research Laboratories) + 2[mu]g. of biotin/day + sulfasuxidine, showed no gain in weight. The same rats were then placed on the same regime but with 20ug./day of crystalline folic acid (Folvite Lederle) for 28 days during which period they showed an avg. gain of 1.3 g./day/rat. They were then returned to the first supplemented diet for 18 days during which period they gained only 0.3 g./day. Other rats on the supplemented diet with folic acid, but without sulfasuxidine gained an avg. of 1.5 g./day/rat. Still other rats did not grow when fed sulfasuxidine, even when given folic acid. Folic aicd is one of the dietary factors necessary for growth of rats on a basal diet with homocystine as the only sulfur-containing amino acid when they are fed sulfasuxidine.