Changes in adrenocortical-pituitary activity in the catfish, Clarias batrachus (L.), after mercury treatment.

The toxic effects of mercuric chloride (HgCl2), emisan 6 (a methoxy-ethyl mercury fungicide), and methyl mercuric chloride (CH3HgCl) on the adrenocortical-pituitary activity of the catfish were investigated after 45, 90, and 180 days of exposure. The adrenocortical cells were highly stimulated in the 90-day HgCl2 group and became hyperplastic in the 180-day group. These cells were active in the 90-day emisan 6 group, with the infiltration of lymphocytes and fibrosis in the 180-day group. In the 90-day CH3HgCl gropu, the cells were active, with lymphocytic infiltration, fibrosis, and necrotic changes in some areas. In the 180-day CH3HgCl group, there was an extensive infiltration of lymphocytes, with localized sites of necrosis and hyperplasia. The ACTH cells in the pituitary were hypertrophied and degranulated in the Hg-treated groups, suggesting increased secretion of ACTH. The plasma cortisol level decreased significantly in the 90- and 180-day Hg-exposed groups in a time-dependent manner. Of the three mercurials, CH3HgCl is the most toxic in reducing the plasma cortisol level in all durations. These results suggest that Hg impairs the adrenocortical-pituitary activity of the catfish.