Effects of two polybrominated diphenyl ethers on rainbow trout (Oncorhynchus mykiss) exposed via food

Two polybrominated diphenyl ethers, 2, 4, 2′, 4′-tetrabromodiphenyl ether and 2, 4, 5, 2′, 4′-pentabromodiphenyl ether were added to the food given to two different groups of rainbow trout. The rainbow trout were fed for a period of 22 days. On days 6 and 22, a number of physiological and biochemical variables were investigated including condition factor, liver somatic index, spleen somatic index, hematocrit, differential count of leucocytes, haemoglobin and glucose in whole blood as well as the liver enzyme activities, glutathione reductase, catalase and ethoxyresorufin-O-deethylase. The results show that both these substances were relatively non-acutely toxic and several variables were unaffected. However, the blood variables hematocrit and blood glucose showed a slight influence from 2, 4, 5, 2′, 4′-pentabromodiphenyl ether after six days of exposure. Also the glutathione reductase activity in the liver decreased after 22 days of exposure. The 2, 4, 2′, 4′-tetrabromodiphenyl ether showed no influence on the investigated variables, with one striking exception. This structure caused a decrease of about 75% in ethoxyresorufin-O-deethylase activity in the liver after six days, and this effect was also observed after 22 days.