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Integrated biomarker responses to dietary polypropylene microplastics in rainbow trout (Oncorhynchus mykiss) under simulated aquaculture conditions
Summary
Scientists fed rainbow trout food containing tiny plastic particles (microplastics) for 45 days and found the fish grew more slowly, with the plastic causing stress and damage in their liver, brain, and other organs, effects that got worse with higher plastic doses and longer exposure. Since farmed trout is a common food fish, this research is an early warning sign that the growing amount of microplastic pollution could affect the health of fish we eat, though more research is needed to know exactly what this means for humans.
Microplastics (MPs) are prevalent contaminants in freshwater ecosystems; however, their effects on ecologically and economically important fish species, such as rainbow trout (Oncorhynchus mykiss), remain poorly understood, particularly from an integrated biomarker perspective. This study evaluated the effects of dietary polypropylene microplastic (PP-MPs) exposure on growth performance, hematological parameters, and tissue-specific oxidative stress responses in O. mykiss. Fish were fed with diets containing 0% (control), 10% (10 PP), or 20% (20 PP) PP-MPs (w/w) for 45 days, with responses assessed at 15-day intervals (days 0, 15, 30, and 45). Growth performance (weight gain, feed conversion ratio, and specific growth rate) and hematological parameters (RBC, WBC, HGB, HCT, MCV, MCH, MCHC, and PLT) were evaluated. Oxidative stress, antioxidant defense, DNA damage, and apoptosis were assessed using SOD, CAT, GPx, GR, GSH, ROS, MDA, 8-OHdG, and Cas-3 in the brain, liver, gill, and muscle, while AChE activity was measured in brain tissue as a neurotoxicity biomarker. PP-MPs residues were detected in the gill and gastrointestinal tissues. Dietary PP-MPs exposure reduced growth performance in a dose- and time-dependent manner, while effects on the hepatosomatic index were transient and the viscerosomatic index remained unchanged. Multivariate analyses revealed significant effects of treatment and exposure duration, with an overall response pattern of liver > brain ≈ muscle > gill, indicating systemic but tissue-specific physiological responses. Biomarker responses were not uniformly significant across tissues, and the observed growth impairment may have been influenced by both PP-MPs-related physiological stress and minor dietary nutrient dilution.