MERCURIC-CHLORIDE AFFECTS PROTEIN SECRETION IN RAT PRIMARY HEPATOCYTECULTURES - A BIOCHEMICAL ULTRASTRUCTURAL, AND GOLD IMMUNOCYTOCHEMICALSTUDY

The toxicity of mercury on hepatocytes was studied at the ultrastructu ral, biochemical, and immunocytochemical levels. Albumin metabolism wa s examined because it is a representative liver-specific function. A n ovel cytochemical method using the protein A-gold technique for the in situ localization of albumin in hepatocyte cultures was applied. Prim ary rat hepatocyte cultures were exposed to increasing HgCl2 concentra tions. Cytotoxicity was assessed by measuring the release of lactic de hydrogenase from the cells. At the highest exposure concentration test ed (50 muM), Hg was found to be significantly cytotoxic in contrast to what occurred at 5.0 and 0.5 muM. The level of albumin secreted, as m easured by ELISA, was decreased by approximately 38% at 5.0 muM HgCl2 and was found not to be different from that of controls at lower conce ntrations. The ultrastructural analysis showed that hepatocytes treate d with 5.0 muM HgCl2 undergo drastic morphological changes such as a d ecreased number of ribosomes associated with the rough endoplasmic ret iculum, and the disappearance of the latter organelle, proliferation o f the smooth endoplasmic reticulum, and dilatation of both the Golgi a pparatus and the biliary canaliculus-like structures. Immunocytochemic al detection of albumin-immunoreactive sites using protein A-gold labe ling further revealed that these were less abundant in hepatocytes tre ated with 5.0 muM HgCl2 (- 64%) as compared to control preparations. T hese results suggest that one of the effects of mercury on hepatocytes is to affect liver-specific functions such as albumin production, pos sibly through interference with ribosomal function. This study also de monstrates for the first time the applicability of the high-resolution protein A-gold technique for toxicological investigations on hepatocy tes in vitro.