Comparative analysis of accumulation of microplastics of various sizes in the rat brain based on an automated morphometric approach

Introduction. Microparticles of plastic (MP) pose a threat to health, but the processes of their accumulation and distribution in living organisms, especially in brain tissues, have not been sufficiently studied. The aim of the study was to compare the accumulation of plastic microparticles of different sizes (100, 500 and 1000 nm) in the brain of rats using a descriptive and quantitative approach. Material and methods. Female Wistar rats, 12 individuals divided into 4 groups, were intracardiacally injected with a suspension of fluorescent polystyrene microparticles (100, 500 and 1000 nm in diameter) or a saline solution (Control) with a volume of 50 µl. The accumulation of microplastics in brain tissues was assessed using fluorescence microscopy using a descriptive approach and a computer program for quantifying the content of microparticles and their conglomerates. The data was analyzed using the Bootstrap method with the Holm–Bonferroni correction, the significance of the differences was determined at p < 0.05. Results. It was found that fluorescent microparticles of plastic accumulate mainly in the cerebral cortex, and the MP 1000 group showed a greater number of clearly defined conglomerates compared to the MP 100 and MP 500 groups. The density of plastic microparticles, estimated using an automated morphometric approach, was also higher in the experimental groups compared with the control, especially in the MP 1000 group. Limitations. The study was limited to studying the distribution of plastic microparticles of three sizes in a toxicological experiment on a single animal species (laboratory rat). The phase of the sexual cycle of female rats was not taken into account. Conclusion. The integration of approaches allows for a deeper understanding of the dynamics of microparticle accumulation: a descriptive approach shows the ability of particles to penetrate the blood–brain barrier (BBB), while a quantitative approach provides data on the content and distribution of particles and conglomerates.