BIOKINETICS AND DOSIMETRY OF CHROMIUM, COBALT, HYDROGEN, IRON AND ZINC RADIONUCLIDES IN MALE REPRODUCTIVE TISSUES OF THE RAT

Following intravenous administration to male rats, the uptake and rete ntion by reproductive tissues of chromium-51, cobalt-57, iron-59, zinc -65 and tritium has been studied for up to 28 days. Chromium-51, Co-57 , Fe-59 and H-3 were not or only transiently accumulated in gonads or accessory sex glands at concentrations greater than whole body concent rations. However, Zn-65 was concentrated in the dorsolateral region of the prostate gland and autoradiography showed preferential uptake by epithelial cells and lumen of glands. When combined with other informa tion available from the literature, this data would suggest that curre nt models adequately describe the biokinetics of chromium, cobalt, iro n and tritium in the prostate and testes and zinc in the testes. Uptak e of zinc by the prostate would appear to be best described by an aver age value of 0.1% and a conservative Value of 0.5%. Allowing for great er uptake of zinc (0.5%) by the prostate, after inhalation of Zn-65 in a soluble form, increases prostate dose by about 3 fold compared to c urrent models. The pessimistic assumptions of a higher relative biolog ical effectiveness (20) for all Anger emissions from Zn-65 in cell nuc lei and a heterogeneous distribution of Zn-65 to sensitive cells in th e prostate increases prostate dose by a further factor of 9. Even on t he basis of these cautious estimates, occupational exposures to radioi sotopes of these elements do not explain the excess of prostate cancer reported amongst some nuclear workers.