Effects of Sublethal Cadmium on Maturation and Testosterone and 11-Ketotestosterone Production in Vivo in Brook Trout

Abstract

A double-isotope derivative assay using [¹⁴C]steroid tracers and [³H]acetic anhydride as tritiating agent was used to determine testosterone and 11-ketotestosterone levels in the blood plasma of male brook trout maintained in freshwater containing 1 ppb cadmium (Cd) and control fish during various stages of sexual maturation. Plasma testosterone and 11-ketotestosterone levels were correlated to approaching period of functional maturity in the control fish, reached a peak of 0.25 and 2.68 µg/100 ml plasma, respectively, and gradually declined with the onset of testicular regression. 11-Ketotestosterone levels (2.34-3.96 µg/100 ml) in Cd-treated fish were higher than in the controls (p < 0.05) and remained elevated during testicular regression. Testosterone levels in the treated fish increased 2 wk later than the control and also remained elevated throughout. There was no apparent effect of the level of Cd used on the onset of secondary sexual characteristics and spermatogenesis but the testes of Cd-treated fish regressed at least 2 wk earlier than the control. The results suggested an impairment in the clearance and/or utilization of testosterone and 11-ketotestosterone by Cd-treated fish. The impaired clearance may also be related to the abnormal vasculature and hemorrhagic necrosis observed in the testes of some of the Cd-treated fish.