VITAMINS

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The effect of NiA on myelination was studied during brain development. 1) NiA-deficient rats and rats receiving 3-acetylpyridine (3-AP) showed lower values in yield of myelin, content of cerebrosides and specific activity of 2', 3'-cyclic nucleotide-3-phosphohydrolase (CNP), when compared with those of pair-fed and ad libitum controls. 2) Despite the changing yield of myelin, the ratio of protein to total lipids, and the percentage composition of lipids were not different between the groups fed on the NiA-deficient and the NiA-supplemented diet. 3) The ratio of long chain nonhydroxy fatty acid (C_<20-24>/C_<14-18>) and synthesis of cerebrosides with nonhydroxy fatty acid were markedly decreased in NiA-deficient rats. 4) The transfer of cerebrosides from the site of synthesis (microsome) to the site of myelin assembly was not impaired in NiA-deficient rats. 5) Biosynthetic activity of lipids in brain slices, and the activities of the microsomal fatty acid elongating system in the brain were decreased in the NiA-deficient rats and rats receiving 3-AP. 6) The rats receiving 3-AP and pair-fed control showed lower values of DNA and RNA in the brain and the concentration of thyroid hormon in the serum when compared with ad libitum control. These results indicated that undernourishment from restricted food intake imposed during the brain development caught up to some extent. Our observations suggest that NiA can influence myelination through the metabolism of cerebrosides which contain long-chain fatty acids.

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Availability of commercial preparations of retinyl palmitate (A-pmt) as a practical standard for high-performance liquid chromatographic (HPLC) determination was studied. A-pmt was determined by the following three methods. (1) Vitamin A assay in JP X (JP method). (2) Purified A-pmt was used as a reference standard (HPLC method). (3) A value of absorbance at 326nm obtained by the JP method was corrected by multiplying it with a ratio of A/T (A: peak area of the peak corresponding to A-pmt by HPLC; T: sum of peak area of all the peaks observed on the chromatogram of HPLC). Since the values obtained by the corrected method on the commercial preparations showed good agreement with those by the HPLC method, we concluded that the preparations were useful as practical standards when the corrected method was used to evaluate the concentration of A-pmt.

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As a standard compounds in studying the metabolism of vitamin D_2, 25-hydroxyvitamin D_2 (25-OH-D_2) bound to vitamin D binding protein (DBP) was isolated and purified from rabbit plasma. A plasma sample obtained from a rabbit which received 500,000 IU of vitamin D_2 was applied to a Sephadex G-200 column, and an eluate containing 25-OH-D_2 bound to DBP was collected and lyophilized. The lyophilized protein fraction was saponified. The resulting unsaponifiable matter was separated and applied to HPLC using a Zorbax SIL column as a stationary phase and 5.5% isopropanol in n-hexane as a mobile phase. The purified compound was identified as 25-OH-D_2 by HPLC, UV spectrum and GC-MS, and confirmed to be useful as as anthentic standard for HPLC assay of 25-OH-D_2. The yield of the purified 25-OH-D_2 was about 30μg from 55ml of rabbit plasma.

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