Is the Beagle Dog an Appropriate Experimental Animal for Extrapolating Data to Humans on Organ Distribution Patterns of U, Th, and Pu?

Abstract

Concentrations and organ distribution patterns of alpha-emitting isotopes of U (238U and 234U), Th (232Th, 230Th, and 228Th), and Pu (239,240Pu) were determined for beagle dogs of our colony. The dogs were exposed to environmental levels of U and Th isotopes through ingestion (food and water) and inhalation to stimulate environmental exposures of the general human population. The organ distribution patterns of these radionuclides in beagles are compared to patterns in humans to determine if it is appropriate to extrapolate organ content data from beagles to humans. The results indicated that approximately 80% of the U and Th accumulated in bone in both species. The organ content percentages of these radionuclides in soft tissues such as liver, kidney, etc. of both species were comparable. The human lung contained higher percentages of U and Th than the beagle lung, perhaps because the longer life span of humans resulted in a longer exposure time. If the U and Th content of dog lung is normalized to an exposure time of 58 y and 63 y, median ages of the U and Th study populations, respectively, the lung content for both species is comparable. The organ content of 239,240Pu in humans and beagles differed slightly. In the beagle, the liver contained more than 60%, and the skeleton contained less than 40% of the Pu body content. In humans, the liver contained approximately 37%, and the skeleton contained approximately 58% of the body content. This difference may have been due to differences in the mode of intake of Pu in each species or to differences in the chemical form of Pu. In general, the results suggest that the beagle may be an appropriate experimental animal from which to extrapolate data to humans with reference to the percentage of U, Th, and Pu found in the organs.

ICRP Publication 137: Occupational Intakes of Radionuclides: Part 3

“…Retention of thorium in the kidneys and its rate of urinary excretion at times remote from injection may have been affected by radiation damage at high dosage levels (Stover et al., 1960). (797) Comparison of the organ distributions of thorium isotopes in humans and beagles exposed to environmental levels alone indicate broad similarities in the long-term distributions of systemic thorium in the two species (Singh et al., 1988). There are also broad similarities in the patterns of distribution and excretion of injected thorium in human subjects (Maletskos et al., 1966, 1969) and beagles (Stover et al., 1960) at early times after administration. (798) The biokinetic of systemic thorium have been studied in various small mammals including rats, mice, guinea pigs, and rabbits (Scott et al., 1952; Boecker et al., 1963; Thomas et al., 1963; Traikovich, 1970; Larsen et al., 1984).…”

“…(797) Comparison of the organ distributions of thorium isotopes in humans and beagles exposed to environmental levels alone indicate broad similarities in the long-term distributions of systemic thorium in the two species (Singh et al., 1988). There are also broad similarities in the patterns of distribution and excretion of injected thorium in human subjects (Maletskos et al., 1966, 1969) and beagles (Stover et al., 1960) at early times after administration.…”

Evaluation of Uranium in Organs of Residents from an Uranium-Rich Region using Teeth as Bioindicators

“…Additionally, the Uranium T c for bones of the residents of Caetité compares well with those obtained with Beagle dogs [19]. In fact, earlier results suggest that the Beagle may be an appropriate experimental animal from which we can extrapolate data to humans with reference to the percentage of U, Th, and Pu found in their organs [20].…”