Physiological effects of levonorgestrel exposure on selected ecological endpoints of Clarias gariepinus

Abstract

Abstract Background Levonorgestrel (LNG) is incorporated into contraceptives and has become a contaminant of emerging concern (CEC) in the pharmaceutical and personal care product (PPCP) category due to its endocrine-disrupting properties; however, its potential to induce physiological aberrations in Clarias gariepinus is yet to be understood. This study examined the impacts of LNG on the pathology, oxidative stress responses and bioaccumulation in C . gariepinus . Results Levonorgestrel induced severe pathological alterations to the gonad, liver, smooth muscle and gill tissues of C. gariepinus . The most prominent pathologies occurred at 10,000 ng L −1 and included primary lamellae aneurysm (gills), dilation of the central vein, vacuolation and steatosis (liver), breakage and disintegration of muscle fibers (muscle). In the female gonads at 1000 ng L −1 , there was evidence of ovotestis in the ovaries, as well as shrinkage of follicles and hardening of the tunica albuginea. Intracellular hydrogen peroxide in the liver of C. gariepinus increased with increasing concentrations of LNG at 10 ng L −1 LNG compared with the controls, but the increase was not significant ( p < 0.05). Malondialdehyde concentration and glutathione S-transferase ( p > 0.05) and peroxidase ( p < 0.05) activities of the liver were elevated in exposed fish. Levonorgestrel bioaccumulated in the smooth muscles of C. gariepinus , with the highest bioconcentration factor of 80 in the third week of exposure to 100 ng L −1 . Conclusion This study demonstrates that C. gariepinus is sensitive to LNG exposure, as reflected in altered histopathology, biochemical components and elevated vitellogenin levels, suggesting endocrine-disrupting effects on the reproductive system, and thus can be effective as a bioindicator in the detection of LNG in aquatic environments.