IN-VITRO DETERMINATION OF AGE-DEPENDENCE OF OXIDATION OF TRITIUM GAS IN RATS

Age dependence of tritium gas (HT) oxidation in rats was investigated in in vitro experiments using faecal suspensions and intestinal conten ts from rats. HT oxidation was determined as the fixation of HT in fae ces or intestinal contents suspended with GAM medium at 30-degrees-C u nder anaerobic and aerobic conditions. The HT oxidation rate in faecal suspension under anaerobic conditions was almost constant irrespectiv e of age and about 10 times that under aerobic conditions in 10 to 100 week old rats. The viable cell number of anaerobic microbes in faeces was 3-4 times that of aerobic microbes (facultative anaerobes) and te nded to decrease with age in each case. The HT oxidation activity of i ntestinal contents was highest in the caecum contents and rectum conte nts under anaerobic conditions, almost the same as that in faeces and nearly constant irrespective of age, and about 10 times that in the re ctum contents under aerobic conditions. The calculated HT fixation rat e (HT --> HTO per g body water) was greatest in 4 week old animals, ab out 4 times that at 2 weeks of age, and showed a slight decrease in ol der animals.