VITAMINS

An improved method was developed for the preparation of thiamine[^<32>P]diphosphate ([^<32>P]TDP) and thiamine[^<32>P]monophosphate ([^<32>P]TMP) of the specific radioactivity of 10 and 5 mCi/mmol, respectively. The purity of those preparations was checked by paper chromatography, high voltage paper electrophoresis, thin layer chromatography, autoradiography and gel filtration chromatography, and found to be more than 93% It took 6 days from the start of phosphorylation to the end of purification. The oxidation product of [^<32>P]TDP and [^<32>P]TMP by BrCN, namely [^<32>P]thiochrome diphosphate and monophosphate, were found to be unstable radiologically. Hence they gave a non-fluorescent radioactive peak amounting to more than 15% of total activity when the oxidation product of pure [^<32>P]TDP or[^<32>P]TMP was developed through a gel filtration column without the addition of a radical scavenger.

View full abstract

Show abstractHide abstract

Vitamin E deficiency of premature infant often induces hemolytic anemia and may be one of the factors resulting in bronchopulmonary dysplasia and retrolental flbroplasia by oxygen therapy. However, vitamin E is poorly absorbed from the gastrointestinal tract of premature infant, so it is necessary to administer vitamin E parenterally when it is required. The purpose of this investigation is to examine the bioavailability of parenterally administered vitamin E. When dl-α-tocopheryl acetate is administered parenterally to the dogs, it enters into the blood stream and then ten percent is hydrolyzed to α-tocopherol in liver and/or other organs. By intramuscular administration of dl-α-tocopheryl acetate (5 mgj/kg), plasma α-tocopherol levels indicated maximal increment of 5.2±3.1 μg/ml with a large individual difference. By intravenous administration of dl-α-tocopheryl acetate (5 mg/kg), plasma α-tocopherol levels indicated a maximal increment of 8.4±1.2 μg/ml without individual difference. However, more than eight hours were required to reach maximal increment of plasma α-tocopherol level, when dl-α-tocopherol acetate was administered parenterally. On the other hand, by intravenous administration of dl-α-tocopherol (5 mg/kg), a maximal increment of plasma α-tocopherol levels (115.2+27.5 μg/ml) and α-tocopherol levels in high density lipoprotein (62.6+11.9 μg/ml) was obtained just after injection. These results suggest that intravenous ad-ministration of dl-α-tocopherol is the most effective method to obtain rapid increment of plasma α-tocopherol levels.

View full abstract

Download PDF (930K)

The mechanism of riboflavin uptake by the human red blood cells was investigated in vitro. The cells were incubated in the physiological saline con taining riboflavin (FR). The uptake of FR showed plateau within 30 min during the time course of the uptake. Apparently the rate of the uptake showed temperature dependency, but no saturation kinetics was found. It was revealed that approximately 75% of ^<14>C-riboflavin transported was converted to FMN and/or FAD within 15 min after incubation and this ratio of FMN plus FAD remained constant until 60 min of the incubation. This result, together with the temperature dependency of the uptake, suggests that two enzymes, flavokinase and FAD pyrophosphorylase, may participate in the uptake of riboflavin. This assumption was supported by the fact that these enzymes were detected in the cytoplasm but not in the erythrocyte membrane fraction. The localization of these enzyme activities also ruled out a possibility of the involvement of group translocation in riboflavin uptake by the red cells. These results suggest that riboflavin passes through the erythrocyte membrane without conformational change and then metabolized to FMN and FAD in the cytoplasm.

View full abstract

Register with J-STAGE for free!