Hepatic steatosis in zebra fish ( Brachydanio rerio) induced by long-term exposure to γ-hexachlorocyclohexane

Abstract

In a full life cycle test, newly hatched eggs of zebra fish, Brachydanio rerio, were reared to sexual maturity under continuous exposure to 40, 80, 110, 130, and 150 μg/liter lindane, γ-hexachlorocyclohexane. The effects of lindane were investigated by recording behavior and survival of the F 0- and F 1-generation as well as morphological alterations in liver ultrastructure of F 0. Changes in peroxisomes were visualized by cytochemical staining for catalase activity with diaminobenzidine. Whereas behavioral changes can already be observed at 40 μg/liter, survival and number of eggs in F 0 as well as survival and growth of F 1 are unaffected by up to 80 μg/liter lindane. At concentrations ⩾ 110 μg/liter, survival of larvae is reduced already after 35 days, and mortality is 100% after 3 months. From 40 μg/liter, liver ultrastructure displays a microvesicular fatty vacuolation (steatosis) characterized by lipid deposition within the cisternae of the RER. At 40 μg/liter, this highly specific pathological change is accompanied by accumulation of hepatic macrovesicular triglyceride droplets, glycogen depletion, and the occurrence of club-shaped mitochondria. Additional alterations at 80 μg/liter comprise proliferation of SER in males and progressive fractionation of RER in females, stacking of club-shaped mitochondria, a conspicuous decrease in peroxisomal catalase activity, infiltration of macrophages into the liver parenchyma, and a significant stimulation of hepatocytic mitosis. Among several substances tested so far in zebra fish (4-nitrophenol, 4-chloroaniline 3,4-dichloroaniline, atrazine, lindane), lindane is the only compound inducing behavioral changes and hepatic steatosis in conjunction with a reduction in fertility. With regard to the relative sensitivity of the methods applied, behavioral and cytological studies appear more responsive to lindane exposure than survival studies.