A Test of Tritium as a Labeling Device in a Biological Study

These experiments demonstrate that an isotopic selection takes place in the over-all direction of the greater retention of the carbon-tritium bond in the utilization of the methyl group of methanol in the biosynthesis of the labile methyl group. A mixture of methanols containing carbon-14, deuterium and tritium has been administered to rats and the isotopic contents of the methyl groups of the choline and creatine isolated from the tissues have been compared with those of the methyl group of the methanol administered. The ratio of deuterium to C14in the choline methyl was 22% of that in the methanol, whereas the ratio of tritium to C14in the choline methyl was 69 to 75% of that in the methanol. Hence one might arrive at quite different interpretations of the possible biological pathways of methanol depending on whether tritium or deuterium was used as the labeling device. © 1952, American Chemical Society. All rights reserved.