Ocular manifestations in niacin deficiency and its reciprocity to riboflavin deficiency.

The following ocular changes were observed in the rabbit in niacin deficiency.(1) Increase, separation, and movement of the pigment at the limbi corneae. (2) Reactive congestion at the limbi corneae and a little corneal vascularization. (3) Separation and movement to rod and cone layer of the pigment at the pigment epithelium. (4) Slight degeneration in the ganglion cells in the retina. Various ocular changes resembling those observed in “Shibi-Gattchaki” patients as well as pellagrins have been produced in niacin deficiency of the rabbit. Further, the following relations between riboflavin and niacin were observed in riboflavin plus niacin-deficient rabbits.(1) In the riboflavin-deficient animals, urinary riboflavin was far less than that of the control animals: urinary riboflavin excretion in the load test was markedly less, indicating a low riboflavin saturation, and the riboflavin levels in the viscera (liver, kidneys, lungs, and heart) were lower than those in the control animals whether riboflavin had been loaded or not.(2) In the niacin-deficient animals, urinary niacin decreased more remarkably than in the control animals, and in the niacin plus riboflavin-deficient animals, urinary niacin fell slightly more than in the niacin-deficient animals. By tryptophan administration, urinary niacin rose temporarily and then fell rapidly till finally disappeared The niacin levels in the viscera of these deficient animals were lower than those in the control animals.(3) Niacin content of the viscera in the niacin plus riboflavin-deficient animals showed seemingly a tendency to decrease more than that in the niacin-deficient animals(4) In the niacin-deficient animals, the riboflavin levels in the viscera were always lower than those in the control animals, whether riboflavin had been loaded or not. From these results it is assumed that niacin and riboflavin compensate for each other, performing synergetic actions in consuming the vitamins in vivo. There may be some other inseparable relationships between the two vitamins, since riboflavin deficiency brought about niacin deficiency.