Environmental concentrations of N-nitrosodiethylamine (NDEA) disturb the Ca2 + and K+ homeostasis in the gills and epidermis of mosquitofish (Gambusia affinis)

N-nitrosodiethylamine (NDEA), a nitrogenous disinfection by-product, is notorious for its ubiquitous presence in the environment and its carcinogenic properties. However, its impact on ion homeostasis in aquatic organisms remains underexplored. In the present study, we investigated the effects of NDEA on ion homeostasis in mosquitofish exposed to varying concentrations for 30 days. Calcium and potassium fluxes were monitored using noninvasive micro-test technology (NMT), and ATPase activities and gene expressions related to ion transport and immune responses were assessed. Principal component analysis was conducted to identify the organs most sensitive to different NDEA exposure levels. The results revealed that NDEA exposure inhibited transport enzyme activities and affected the expression of ion transport- and immune-related genes. Among all tested tissues, the gills exhibited the highest overall sensitivity (0.443) to NDEA exposure, underscoring their essential functions in ion transport and calcium regulation. These findings underscore the critical role of ion homeostasis in NDEA-induced toxicity and highlight the importance of understanding tissue-specific responses in assessing the ecological risks posed by N-nitrosamines in aquatic environments.