The effect of sublethal cyanide exposure on plasma viteliogenin levels in rainbow trout (Salmo gairdneri) during early vitellogenesis

Female rainbow troutSalmo gairdneri were exposed to 0.01 mg L^–1 hydrogen cyanide (HCN) for 12 days at 12.5 ± 0.5C at the onset of vitellogenesis (May–June). Plasma vitellogenin levels were measured, utilizing a homologous radioimrnunoassay specifically developed for this species. Exposure to HCN reduced vitellogenin levels in the plasma to levels recorded in the control non-vitellogenic group. Similarly, the gonadosomatic index declined steadily throughout the experimental period in vitellogenic females exposed to cyanide while no difference was observed in hepatosomatic indices relative to controls. The high sensitivity of the radioimmunoassay for vitellogenin utilized in this study has permitted a rapid assessment of the effects of low levels of this toxicant on yolk production. The findings indicate that exposure of naturally reproducing female rainbow trout to this low concentration of HCN during early vitellogenesis would eliminate an important source of yolk precursor synthesized in the liver and sequestered by the ovary.