Examination of Testicular Tumours in the Beagle Dog Exposed to Inhaled Plutonium

Abstract

Gross and light microscopic features of testicular neoplasms were examined in the male beagle dog used in three studies to examine the life-span effects of inhaled plutonium (Pu). One hundred and sixty-six cases of testicular neoplasia (TN) occurred among 105 dogs that ranged in age from 7·5 to 17·7 years at the time of diagnosis. The 166 cases of TN comprised 113 interstitial cell tumours, 27 seminomas in situ, 19 seminomas, and seven Sertoli cell tumours. Serum testosterone and estradiol 17-β concentrations, and the serum testosterone-to-oestradiol ratio were determined in 39 dogs with TN and in five clinically normal, sexually intact, age-matched cohorts. Serum hormone concentrations did not differ significantly among tumour types or between dogs with neoplasms and age-matched cohorts. There was a significant relationship between initial lung deposition (ILD) of Pu and activity in the testis (Bq/g testis). The slope of the relationship was 0·35, 0·89 and 0·91 for ²³⁹PuO₂, ²³⁸PuO₂ and ²³⁹Pu(NO₃)₄ respectively. Pu in the testis at long times (> 5 years) after inhalation was between 0·0001 and 0·03% ILD, depending on the physicochemical form of Pu. Although the mean activity of Pu in the testis of dogs was higher in those life-span studies employing ²³⁸PuO₂ and ²³⁹Pu(NO₃)₄, the cumulative proportion of dogs with tumours, the distribution of tumour types, and mean time to first tumour was not significantly different among the three studies or dose groups, including controls, within a study.