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

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 micrograms/liter lindane, gamma-hexachlorocyclohexane. The effects of lindane were investigated by recording behavior and survival of the F0- and F1-generation as well as morphological alterations in liver ultrastructure of F0. Changes in peroxisomes were visualized by cytochemical staining for catalase activity with diaminobenzidine. Whereas behavioral changes can already be observed at 40 micrograms/liter, survival and number of eggs in F0 as well as survival and growth of F1 are unaffected by up to 80 micrograms/liter lindane. At concentrations greater than or equal to 110 micrograms/liter, survival of larvae is reduced already after 35 days, and mortality is 100% after 3 months. From 40 micrograms/liter, liver ultrastructure displays a microvesicular fatty vacuolation (steatosis) characterized by lipid deposition within the cisternae of the RER. At 40 micrograms/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 micrograms/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.