Vitamin A metabolism. I. Vitamin A contents of blood serum and breast milk in infants and lactating mothers. II. Vitamin A loading test on healthy infant. III. Effect on the liver of intravenous administration of vitamin A
Bitamin 13: 175-189
Vitamin A (I) level in blood serum of healthy 8-year-old humans was less than that of those above 9 years, and av. level was 104 I.U./100 ml. I level in weak and healthy infants was the same. Correlation coeff. was 0.69 in lactating mothers receiving I prepns., but no correlation was observed in those receiving no vitamin except the contents of I in serum and in milk. The administration of I showed the influence more clearly on the vitamin content of milk than on that of blood serum. II. Examns. of the changes of I level in serum after the administration of I prepns. to healthy infants showed that in those receiving the oily or aq. prepn. intramuscularly the change was irregular as compared with those receiving the aq. prepn. per os. The oral administration of aq. I prepn. seemed to be better absorbed than parental administration. The transition of I into spinal fluid in the infants suffering from tuberculous meningitis with an increased permeability of the spinal membrane (after administration of 50,000 I.U. of aq. I prepn.) was not observed, while only 0.5% of loading amt. was detected in feces. III. Dogs were used. I value of blood of hepatic vein was always lower than that of the artery after the administration, while inflow of I into the liver was observed. Two hrs. later the blood levels of hepatic vein and artery were both high. This suggests that the deposition of I in the liver might be difficult in a nutritional sense. In animals receiving a relatively small amt. of I, the retention of I in liver seems to be easier.