New nephron development in fish from polluted waters: a possible biomarker.

: Recent evidence has shown that fish have the ability to develop new nephrons following renal injury. This study evaluated the usefulness of quantifying developing nephrons in mature fish as an ecotoxicological assessment tool. Histological sections of kidney were prepared from Atlantic tomcod and brown bullhead specimens collected from reference and contaminated streams. The numbers of developing nephrons and basophilic cell clusters from which the nephrons arise per section area were determined by image analysis. The numbers of basophilic clusters and developing nephrons in tomcod kidney were found to be one to two orders of magnitude higher than for the bullhead. In tomcod from the Hudson River, the number of both basophilic clusters and developing nephrons were elevated relative to samples from the less contaminated Saco and Royal Rivers. In bullheads, when analysis was conducted over several seasons, the number of basophilic clusters and developing nephrons from Cuyahoga River samples were elevated relative to samples from the less-contaminated Old Women Creek and Toussaint River. Developing nephrons and basophilic clusters seem to have potential as general indicators of ecological condition, but may be better suited for detection of nephrotoxicity at specific sites.