Toxic effects of microplastic (polyethylene) on accumulation, hematological parameters and antioxidant responses in...

In this study, Cyprinus carpio nudus were exposed for 2 weeks to polyethylene microplastics (MPs) of two particle sizes (125 μm and 34 μm) at concentrations of 0, 40, 80, 160, 320, and 640 ppm. The experiment involved 11 treatment groups, each with triplicate tanks, and evaluated MPs accumulation in tissues, hematological profiles, plasma components, and antioxidant responses. Accumulation in the gill, intestine, and liver were quantified using Nile red staining and fluorescence microscopy, showing the highest accumulation in the intestine, followed by the gill and liver, with smaller MPs accumulated significantly more than larger MPs. Exposure to MPs resulted in significant changes in hematological parameters (red blood cell counts [RBC], hemoglobin [Hb], hematocrit [Ht]), plasma components (calcium, magnesium, glucose, cholesterol, total protein [TP], aspartate aminotransferase [AST], alanine aminotransferase [ALT], alkaline phosphatase [ALP]), and antioxidant responses (superoxide dismutase [SOD], catalase [CAT], glutathione S-transferase [GST], reduced glutathione [GSH]), and smaller MPs induced significant changes at lower exposure concentrations. In particular, AST, ALT, CAT, GST, and GSH showed significant differences depending on MP particle size, primarily at specific high concentrations (340 and 640 ppm) rather than uniformly across all concentrations, suggesting that smaller MPs demonstrate higher toxicity. Principal component analysis (PCA) and integrated biomarker response (IBR) analyses further supported that both concentration and particle size influence MPs toxicity, with PCA demonstrating distinct separation among exposure groups and greater physiological deviations in fish exposed to smaller MPs, and IBR indicating more pronounced overall biological responses at higher concentrations, particularly for smaller MPs.