Detection of Diclofenac‐Induced Alterations in Rainbow Trout (Oncorhynchus mykiss) Using Quantitative Stereological Methods.

This article focuses on the ecotoxicological effects of the nonsteroidal anti-inflammatory drug diclofenac (DCF) on rainbow trout (Oncorhynchus mykiss) through a 28-day exposure experiment using environmentally relevant concentrations. The study applied unbiased quantitative stereological methods to assess histomorphological changes in gills and trunk kidneys, revealing significant increases in gill secondary lamella thickness and interstitial renal tissue volume at DCF concentrations of 25 µg/L and above, while decreases in nephron volume were observed at concentrations as low as 0.5 µg/L. Additionally, plasma levels of prostaglandin E2 (PGE2), a biomarker linked to DCF's mode of action as a cyclooxygenase inhibitor, significantly decreased at concentrations ≥0.5 µg/L in males and ≥1.0 µg/L in females. These findings indicate that DCF induces subtle but measurable physiological and morphological effects in fish at concentrations commonly found in surface waters impacted by wastewater effluents, underscoring the need for improved wastewater treatment to mitigate environmental risks.