Influence of age at exposure on concentrations of 239Pu in beagle gonads

The influence of age at injection of 239Pu on the gonadal concentrations with time after injection in beagle dogs was determined. In addition, the distribution patterns of Pu within the organs were examined using fission track autoradiography. Beagles of different ages (juveniles approximately 90 d; young adults approximately 17 mo; aged approximately 5 y) were given a single injection of 239Pu(IV)-citrate and most were allowed to live out their natural lifespan. At times greater than 1,000 d after exposure, the concentrations of 239Pu (expressed as percent injected per gram organ weight) were higher in the testes and ovaries from animals injected as young adults (median 9.8 X 10(-4) and 15.4 X 10(-4%) g-1, respectively) when compared with the juveniles (median 2.8 X 10(-4) and 7.7 X 10(-4%) g-1, respectively) or aged (median 6.3 X 10(-4) and 17.2 X 10(-4%) g-1, respectively) animals. The lower concentrations found in the animals injected as juveniles can be attributed to the increase in gonadal size that occurs during organ maturation and puberty. Fission track autoradiographs from gonadal tissues at least 5 y after exposure confirm the nonuniform distribution of the nuclide in these organs. In the testis, Pu was found mostly in the interstitial tissues and in the ovary, was found in the stroma, particularly the medullary stroma.