Abstract
This study was undertaken to determine whether the concentration of vitamin A in the blood has any relationship to the vitamin A intake and to the storage in the liver. Groups of albino rats, 3 to 4 weeks of age, were fed amounts of vitamin A ranging from 0 to 1000 international units daily. The vitamin A supplement used for rats receiving 100 units or less daily was a reference cod liver oil obtained from the United States Pharmacopea Committee, whereas rats receiving 1000 units were given a vitamin A concentrate. After the rats received these preparations for 6 weeks, the vitamin A content of their bloods and livers was determined 24 hours after the last dose of the vitamin.
The method employed for the vitamin A determination of the blood and liver was based on the Price-Carr reaction. As the diet was devoid of carotene, this substance was not found in the blood or livers of the rats. The vitamin A in the blood was extracted directly with petroleum ether and alcohol as recommended by Clausen and McCoord, 1 whereas the liver was treated by a preliminary saponification. The extracts were evaporated in nitrogen. taken up with chloroform and then treated with antimony trichloride. The intensity of the resulting blue color was measured at 620 μM with the use of an Evelyn Photoelectric Colorimeter. 2 The reading was translated into biological units (international) by referring to a calibration curve obtained with a sample of halibut liver oil of known biological potency.
The relationship of the vitamin A blood level to vitamin A intake and to liver storage may be noted in Table I. It will be observed that when the intake was less than 50 units daily the vitamin A concentration of the blood was directly related to the vitamin A intake.
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