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Part of the bile acid synthesis takes place in peroxisomes. An altered enterohepatic circulation of bile acids might influence peroxisomal beta-oxidation enzymes and peroxisomal morphology. We performed a morphological and morphometric investigation of peroxisomes in liver biopsy samples of eight patients with cholestasis of different origin: graft versus host reaction (n = 1), obstruction of the bile flow (n = 3), and drug-induced cholestatic hepatitis (n = 4). Peroxisomes were identified using catalase cytochemistry. They were regularly shaped and showed individual differences in electron density. A perinuclear distribution was observed in a variable number of hepatocytes in each sample. Morphometric analysis of peroxisomes revealed an increase in numerical density and surface density in all, and a decreased mean diameter in four liver samples. Based on previously obtained data in experimental animals, we hypothesize that the observed alterations in peroxisomal morphology indicate an enhanced metabolic activity of the enzymes in the peroxisomal matrix. Among them are enzymes involved in bile acid synthesis.

An increased H2O2 production and a decreased activity of several peroxisomal oxidases have previously been reported in kidneys of rats with five-sixth nephrectomy, a model for chronic renal failure. We investigated the morphological and morphometric characteristics of peroxisomes, the organelles in which an important part of cellular H2O2 metabolism is localized, in remnant kidneys 16 weeks after operation. The vast majority of renal peroxisomes were found in the epithelial cells of proximal tubules. The organelles were distributed throughout the cells. We observed a significant increase in size, perimeter and volume density of the peroxisomes as compared to normal kidneys. Elongated peroxisomes were less frequent. An inverse linear correlation between mean size and number of peroxisomes was found. In cortex homogenates, the activity of catalase the peroxisomal H2O2-scavenging enzyme, was significantly decreased and was inversely proportional to the mean peroxisomal diameter. The observed morphological adaptations are believed to create an unfavorable situation for the enzymatic activities in remnant kidney peroxisomes.