Histopathology of kidney of Channa punctatus exposed to chronic nonlethal level of Elsan, mercury, and ammonia.

Histopathological changes in the head and trunk kidneys of Channa punctatus induced by chronic nonlethal levels of Elsan (211 ppb), mercuric chloride (16.7 ppb), and aqueous ammonia (15.64 ppm) were studied on 7, 28, 63, and 90 days of exposure. The pathology of the head kidney was characterized by degeneration and dispersion of interrenal and chromaffin tissue and necrosis in the haemopoietic elements. Kidney lesions were observed throughout the entire experimental period in fish exposed to Elsan and mercuric chloride. In contrast, the lesion induced by exposure to aqueous ammonia began to heal during the first phase of treatment. Marked abnormalities in trunk kidney histology were also found. Renal lesions consisted of minimal to mild multifocal, acute tubular epithelial degeneration, karyolysis, and dilation or shrinkage of Bowman's capsule and glomerulus. Elsan treatment resulted in a highly significant decrease in the dimension of Bowman's capsule and glomerulus at all days of sampling, except on Day 28. The response of the fish trunk kidney tissue to mercuric chloride was similar to that observed with Elsan exposure in terms of the alteration in the mean dimensions of Bowman's capsule and glomerulus. The response to ammonia was significant reduction in the size of Bowman's capsule and glomerulus throughout the experimental period except at Day 28. Little dilation of Bowman's capsule and a significant dilation of glomerulus were found at Day 28 of ammonia exposure. This study demonstrated that a chronic nonlethal exposure to Elsan, mercuric chloride affect both endocrine and excretory parts of the kidney while ammonia specifically damages the excretory part of the kidney of C. punctatus.