Heavy metal induced protein synthesis in fish cell lines.

The regulation of heavy metal induced gene expression was investigated in two fish cell lines: the rainbow trout hepatoma (RTH) and Chinook salmon embryo (CHSE) cells. The induction of metallothionein (MT) synthesis occurred in RTH cells exposed to zinc, and to a lesser extent, following exposure to cadmium. The time courses of MT synthesis were different for the different metal inducers, suggesting that MT may be differentially regulated in these cells. CHSE cells, unlike RTH cells, did not synthesize MT in response to metal treatment. Treatment of the cells with 5-azacytidine prior to heavy metal exposure resulted in the induction of MT synthesis. Since these cells were embryonic in origin, these findings raised the possibility that MT gene expression may be developmentally regulated in fish. Analysis of the entire spectrum of cellular proteins has revealed the synthesis of an unknown, 14,000 dalton, metal-inducible protein (MIP) and various stress proteins following exposure of fish cells to heavy metals.