Gentamicin-induced nephrotoxicity and nephroneogenesis in Oreochromis nilotica, a tilapian fish

The renal response to 2 doses of gentamicin (low dose of 5 mg kg-' of body weight and high dose of 25 mg kg-' of body weight) was examined in the tilapian fish Oreochromis nilotica. Gentamicin exposure induced acute tubular necrosis that peaked in severity at 2 d following intraperitonea] injection of the high dose and at 4 to 7 d following injection of the low dose. Necrosis following high dose exposure was more severe than that following low dose exposure. Histochemical staining for gamma glutamyl transpeptidase showed the site of injury to be localized in the proximal tubules. Immunohistochemical staining with 5-bromo-2'-deoxyuridine was used to mark cell proliferation during regeneration and nephroneogenesis. Regeneration of epithelia1 cells along the basement membrane of damaged tubules and development of new nephrons were both documented following nephrotoxic injury. Although the overall pattern of renal response to gentamicin exposure was similar to that which has been previously documented in other freshwater fish species, the commercially important tdapian fish was significantly more sensitive than other fishes.