Small cytoplasmic bodies in the loop of Henle and distal convoluted tubule that resemble peroxisomes

Renal peroxisomes are believed to be restricted to the proximal convoluted tubules. However, we have found particles in the loop of Henle and distal convoluted tubule that resemble the peroxisomes of the proximal tubules in some respects. Although smaller in size (generally too small to be resolved in the light microscope), they have a finely granular homogenous matrix and are delimited by a single unit membrane. Whether these are microbodies (peroxisomes) or dense bodies (lysosomes) cannot be determined solely on the basis of their fine structure. These bodies do not show acid phosphatase activity, indicating that they are not lysosomes. When incubated in a diaminobenzidine medium that demonstrates the peroxidatic activity of the peroxisomal enzyme catalase, the small bodies are reactive, suggesting that they are peroxisomes. This activity is blocked by 3-amino-1,2,4-triazole, an inhibitor of catalase.