Technetium absorption and turnover in monogastric and polygastric animals.

Technetium (Tc) released into the environment can reach animals in various chemical forms: as pertechnetate (TcO-4) in drinking water or deposited on the surface of vegetables and forage plants, or as Tc bioincorporated into plants and associated with various plant constituents. In addition to being influenced by chemical speciation in the diet, absorption, metabolism, and retention of Tc in animals are modified by the treatment that the alimentary bolus undergoes during its passage through the gastrointestinal tract. This behavior differs markedly between polygastric and monogastric animals. We have, therefore, studied the fate of 99mTc given in the diet either as TcO-4 or bioincorporated into maize in rats (as an example of a monogastric animal) and in sheep (as an example of a polygastric animal). Urine and feces were collected and assayed for Tc activity by gamma spectrometry. Animals were sacrificed at different times after contamination, and the Tc content of tissues was determined. The pattern of absorption, excretion and, to a certain degree, of organ distribution and retention depended on animal species and species of Tc administered. Excretion was by feces and urine, and several metabolic components could be discerned. A component of very short half-time in urine suggests that newly absorbed Tc is more readily excreted than that already bound by tissues. The highest tissue concentrations were found in the thyroid. Retention of Tc was, however, most pronounced in bone and skin. Hair contains considerable amounts of Tc and may serve as a bioindicator of Tc contamination.

Metabolism of 51Cr, 54Mn, 59Fe and 60Co in lactating dairy cows.

Different radionuclides which can be released by nuclear installations (Na2(51) CrO4 , 54MnCl2 , 59FeCl3 and 60CoCl2 ) were given to lactating dairy cows either orally or by intravenous (i.v.) injection. Excretion into feces and urine as well as secretion into milk were followed for several weeks. Distribution of activity in organs was determined at sacrifice 102 days after oral and 70 days after i.v. administration. After ingestion, excretion of chromate followed a three-term exponential function with half-lives of 0.88, 3.7 and 26 days. Intestinal absorption was on the order of 0.1-0.2%. About 63% of injected chromate was excreted into urine, about 18% into feces and about 3.6% into milk. Orally administered chromate was concentrated in liver, intestine and spleen. The transfer coefficient into milk was about 1 X 10(-5) days/1. Less than 1% of an ingested dose of manganese was absorbed. Excretion occurred mainly into feces and followed a three-term exponential function. Very little manganese was excreted into urine or secreted into milk. Manganese is concentrated in brain, pancreas, kidney and heart but the differences in concentration are small. The body burden is, therefore, mainly determined by manganese in muscle, skin and bone. The transfer coefficient of manganese into milk is about 3 X 10(-5). Excretion of iron into feces after oral administration follows a three-term exponential function with a small component having a half-life of 72 days. Intestinal absorption is on the order of 0.5-2% of the dose. After i.v. administration, 7% of the dose is excreted in the feces displaying two components of turnover. Very little iron is excreted into urine. Secretion into milk also follows a two-term exponential function. The transfer coefficient of iron into milk is about 3 X 10(-5). About 0.6% of an oral and about 94% of an i.v. dose were recovered from the cows at sacrifice. Most activity was present in blood, liver and spleen. Excretion of radiocobalt into feces after oral administration is described by a three-term exponential function, while excretion into milk and urine is described by two-term exponential functions. Long-lived components in urine and milk represent about 5-10% of the activity absorbed. Only 1-2% of an oral cobalt dose is absorbed and 0.05% of an oral and 5.85% of an i.v. dose is recovered from the cow at sacrifice where concentrations are highest in kidney and thyroid. The body burden depends mainly on cobalt in muscle, skin and bone. The transfer coefficient of cobalt into milk is about 7.5 X 10(-5).

Distribution of tritium in the different organs of calves and pigs after ingestion of various tritiated feeds.

A research programme on the transfer of tritium in the food chain has been in progress for several years on the experimental farm of the Nuclear Energy Research Center at Mol. The studies reported here are related to the distribution of tritium in the organs of farm animals contaminated in various ways. Two young male calves ingested tritiated milk; the daily intake of 3H-organic form was about 15 muCi for each calf and the total activity ingested until the sacrifice was 482 muCi. Three male pigs from the same litter and about 7 weeks old were used for each experiment on the administration of tritium under different forms: (a) single intraperitoneal injection of 39.3 mCi HTO (P2, P3, P4). (b) daily ingestion of 28.4 muCi HTO. The total activity ingested was respectively 569 muCi (P5) and 766.8 muCi (P6). (c) ingestion of tritiated potatoes. The total activity ingested was respectively 21 muCi (P8), 40.3 muCi (P9) and 48.1 muCi (P10). (d) ingestion of tritiated milk powder. The total activity ingested was respectively 60.6 muCi (P13), 110.4 muCi (P11) and 154.5 muCi (P12). After slaughtering of each animal various organs were removed and analyzed for the 3H content in the tissue water and in the organic matter. We could verify that the chemical form of 3H present in the food is of great importance for the incorporation of 3H in the organic matter of the animal organs. The total incorporation increases by a factor 5.6 when 3H is ingested as tritiated milkpowder by pigs as compared to HTO and with a factor 15 for calves. When tritiated potatoes were ingested by pigs a factor 15.6 was found. The transfer of 3H from HTO and milk feed ingested in the organic fraction of organs is lower for pig than for calf. When we consider the 3H in the tissue water of organs the specific activity (SA) is a little lower than the SA of ingested HTO and after ingestion of tritiated milk feed the activity is very low and no difference due to the species is found. After fractionation of liver and spleen tissue following the technique of Schmidt--Thannhauser radioactivity was found in all liver and spleen constituent lipids--RNA--DNA and proteins, but after isolation and purification of DNA following the original methods, we have not been able to demonstrate that tritium is really incorporated into DNA molecules of a non-dividing organ such as the liver nor of an actively dividing organ such as the spleen.