The Cellular Approach to the Determination of Pyridoxine Requirements in Pregnant and Nonpregnant Rats

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Abstract
The cellular approach was used in evaluating the pyridoxine requirements of pregnant and nonpregnant rats. A plateau in hepatic DNA and RNA concentrations occurred at the 10 µg level of pyridoxine intake in nonpregnant animals. The DNA concentration of maternal and fetal livers also plateaued at the 10 µg level, whereas the DNA content of fetal brain did not plateau until 15 µg. RNA concentrations in fetal and maternal liver also plateaued at the 15 µg level. Hepatic polysomal activity maximized in animals fed the 10 µg level of pyridoxine; however, fetal brain ribosomal activity did not plateau until the level of intake was 20 µg. Total protein content was related to polysomal and ribosomal activities; a plateau in protein content in maternal and fetal liver occurred at the 15 µg level of pyridoxine intake and in fetal brain at 20 µg. Among the measurements used, alanine aminotransferase activities, protein and RNA content, and polysomal activities had the highest correlations with the level of pyridoxine intake. On the basis of these parameters, the pyridoxine requirement for nonpregnant rats appeared to be between 10 and 15 µg daily and between 15 and 20 µg for pregnant animals.