Polystyrene microplastics: a threat to renal energy metabolism and tissue morphology in Wistar rats

As a detoxifying organ, the kidney collects polystyrene microplastics and demonstrates significant changes in energy metabolism. The present study aims to evaluate the effect of polystyrene microplastics on renal energy metabolism and tissue architecture by a dose-dependent study. Male Wistar rats were given polystyrene microplastics (PS-MPs) orally at doses of 0.5 mg/L, 5 mg/L, and 50 mg/L for four weeks. After sacrifice, blood glucose, tissue pyruvate level, TCA cycle enzyme functions, glucose 6-phosphatase, lactate dehydrogenase, and transaminase enzyme activities, as well as tissue histology were performed. It was revealed that PS-MPs affected food consumption patterns, causing hypoglycemia. Glycolysis was impaired, as demonstrated by decreased pyruvate level. TCA cycle enzyme functions were stimulated in the kidneys to sustain energy levels in hypoglycaemic conditions. PS-MPs suppressed glucose 6-phosphatase action, indicating reduced gluconeogenesis. Increased lactate dehydrogenase action may enhance pyruvate to lactate synthesis, causing a metabolic shift toward anaerobic stress. Other changes were decreased acidic protein and free amino nitrogen contents and transaminase activities, specifying tissue injury. Histopathological changes demonstrated diminished Bowman’s capsular space and tubular edema at low-dose exposure. The renal medulla showed nuclear pleomorphism and migration in tubular epithelial cells. Furthermore, Bowman’s capsular gap disappeared with the medium dose. Tubular inflammation and disruption in normal medullary architecture were evident. The highest dose revealed drastic tubular inflammation and complete disappearance of Bowman’s capsular space in the renal medulla. It is concluded that PS-MPs at the current doses and duration caused remarkable alteration in renal bioenergetics associated with histopathological disharmony.