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Studies on Carotenoid Metabolism

X. The Site of Conversion of Carotene to Vitamin A in the Chick¹

Department of Biochemistry and Nutrition, University of Southern California, Los Angeles

When ß-carotene was fed to vitamin A-depleted chicks, vitamin A first appeared in the intestinal wall after one hour and in the liver after three hours.

The proportion of vitamin A per gram of tissue was constantly higher in the intestinal wall than in the liver for a 6-hour period after the feeding of carotene.

When massive doses of vitamin A were fed to chicks, the amount of vitamin A in the intestinal wall fell to a relatively insignificant level on the second day in spite of the fact that the concentration of vitamin A in the liver was extremely high. It is believed that this fact means that the presence of large concentrations of vitamin A in the liver does not cause a concomitantly high concentration in the intestinal wall.

These data are interpreted as proof that the chick is able to change ß-carotene to vitamin A in the intestinal wall.

Manuscript received 20 March 1950.