The use of (3H) thymidine-adsorbed on activated charcoal for the study of non-premitotic DNA synthesis in newborn rat hepatocytes.

DNA synthesis in newborn rat hepatocytes was studied in the first three days of life by means of repeated injections of (3H) thymidine. One group of animals was treated with the label adsorbed on activated charcoal (experimental group) and another group (controls) was given the label diluted in saline. The specific activity of DNA was higher in control group, but its increase was not linear with time; in the experimental group, the radioactivity was lower, but its increase with time was linear. The percentage of labeled nuclei was higher in the experimental animals than in the controls and increased linearly with time. The average number of grains/nucleus was considerably smaller in the experimental group than in the controls, in which also the percentage of labeled cells showed considerable variations during the first three days of life. It is concluded that activated charcoal adsorption increases label availability with time and, by keeping a lower label concentration in the pool, reduces the risk of radiation damage.