Technetium Absorption and Turnover in Monogastric and Polygastric Animals

Abstract

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.

99Tc transfer from water to monogastric

“…We obtained transfer factors of 0.05 for kidneys, and 0.07 for the liver. This result is close to those to Gerber et al [6] and Jones [1] from which we calculated respective transfer factors of 0.07 and 0.05 for the kidneys, and 0.08 and 0.03 for the liver. On the other hand, if we are interested in tissues where the balance is not reached, we can give as indication a "temporary" transfer factor of 4.27 for the thyroid and 3.38 for the…”

“…The single exposure underestimates the real uptake of Tc by these tissues. Indeed, Gerber et al [6] obtains transfer factors of only 1.4 and 0.1 for the thyroid and the hair, respectively.…”

Negligible clearance of ultrafine particles retained in healthy and affected human lungs

“…The second estimate of leaching was performed by measuring activity in urine [14,15] from the subjects sampled during the first 24 h after exposure. classifier model 3071, condensation particle counter (CPC) models 3010 and 3020).…”

“…Presence of oxygen during particle generation produces pertechnetate ( 99m TcO 4-), which instantaneously leaches off the labelled particles in body fluids [17][18][19]. Pertechnetate assembles in the thyroid and is excreted with urine within days [14,15]. This may contribute to the results interpreted as translocation in the study by NEMMAR et al [11], in which thyroid glands and bladder were visible in the whole body scan.…”

The effects of plant traits and phylogeny on soil-to-plant transfer of 99Tc

“…Here we analyse interspecies differences in 99 Tc transfer from soil-to-plants to aid assessments of 99 Tc behaviour in the environment. Technetium-99 released into soils has the potential to contaminate food chains, although its radiological effects are normally only considered to be significant at very high activities (Gerber et al, 1989). In a review of data generated prior to 1983, Coughtrey et al (1983) concluded that transfer of 99 Tc from soil-to-plant was affected by soil factors, and by intra-species and inter-species effects.…”