Studies with oxythiamine to mimic reproduction disorders among fish early life stages

Newly fertilised eggs of sea trout (Salmo trutta) were injected with the thiamine antagonist oxythiamine or with oxythiamine in combination with 3,3′,4,4′-tetrachlorobiphenyl (PCB #77). Rainbow trout (Oncorhynchus mykiss) eggs were injected with PCB #77. A decrease in liver transketolase activity was used as a biomarker to indicate a physiological deficiency in thiamine. Exposure to oxythiamine caused deformities in the newly hatched larvae, as well as high mortality during the larval stages. Exposure to oxythiamine in combination with PCB #77 caused a synergistic higher frequency of disorders. Analysis of liver transketolase activity in the larvae injected with PCB #77 indicated that PCB #77 did not decrease the half-life of thiamine in the offspring. The data obtained indicate that oxythiamine increased the sensitivity to PCB #77 in the offspring, however through mechanisms other than those causing thiamine deficiency in feral fish.