Autoradiography of the water compartments in developing teeth of young mice

The distribution of [14C-a1acetyl-4-aminoantipyrine ([14C]NAAP), as indicators of total tissue water, and [carboxy-14C]inulin ([14C]inulin), as an indicator of extracellular water, were studied by autography in mice 4-16 days old. An autographic technique was used that does not translocate or remove the radioactive material. Photometric densities of the autoradiographs revealed wide variations in radioactivity among the various areas of the teeth. Evidence for binding of [14C]urea to bone limits the usefulness of this compound as an indicator. Although [14C]inulin appeared to be a reliable indicator, it is difficult to correlate its distribution with the progress of mineralization determined by electron microprobe analysis. [14C]NAAP was considered to be the most reliable indicator; it revealed that the water content of various areas of the teeth ranged from 7 to 100% of that in blood.