Tritium metabolism in young pigs after exposure of the mothers to tritium oxide during pregnancy

Pregnant sows were given tritiated water at two different doses (0.517 and 1.53 mCi/liter) during pregnancy and for 43 days thereafter (a total of 120 days). Some of the young pigs were left with their mother while the others were exchanged with uncontaminated newborns to follow tritium oxide and organic tritium in different organs with respect to (a) continuing uptake, (b) uptake from milk, and (c) loss of activity after birth. Turnover time of tritium oxide in adult sows is almost 10 days, and that in young pigs is about 8 days. In addition, components (≤5%) of slower turnover are present. At equilibrium, the relative specific activity (i.e., the ratio of specific activity of tritium oxide isolated either directly or after combustion of organic matter to the specific activity of tritiated water ingested) is about 0.7 for body water in adult and newborn pigs and about 0.14 for organic tritium in most tissues. It is somewhat higher (0.22) in the brain of newborns than in other tissues. Turnover time for organic tritium in young pigs is longest in brain (59 days) and slower in muscular tissues (28 days), kidney, spleen, and pancreas (22 days), and liver and intestine (17 days). From the data presented it is estimated that the contribution of organic tritium to the integral tissue dose is on the order of one-third to two-thirds of that from tritium oxide alone, except in the case of brain, where the contribution to the dose from organic tritium may equal or even exceed that from tritium oxide.