OBSERVATIONS ON HEPATIC AND RENAL PEROXISOMES (MICROBODIES) IN THE DEVELOPING CHICK

Peroxisomes (microbodies) in developing liver and metanephric kidney of the chick were studied with a staining method that visualizes these organelles by light and electron microscopy. In both tissues nucleoid and anucleoid peroxisomes were evident at all stages studied (15th day of incubation to the adult). Hepatic peroxisomes showed no special topologic relationship to glycogen areas and were mainly confined to other areas of the cytoplasm. Nucleoid type peroxisomes were more apparent before and after hatching and rarely observed in the adult. Peroxisomes were present in kidney proximal tubule cells, but absent from cells of distal convoluted tubules. They appeared to increase in number during development and were most conspicuous in the adult. The structure of the nucleoid in renal peroxisomes resembled that of the hepatocyte but contained a more distinct series of parallel dense laminae. Diaminobenzidine (DAB) oxidative activity, although relatively weak, visualized nucleoid and anucleoid peroxisomes in liver and kidney at all stages of development. Anucleoid peroxisomes could be distinguished from various dense bodies in hepatocytes and from droplets in proximal convoluted tubule cells, both of which lacked DAB oxidative activity. The DAB reaction in peroxisomes was not suppressed in the absence of hydrogen peroxide or in the presence of the catalase inhibitor, 3-amino-1,2,4 triazole. DAB reaction, sensitive to potassium cyanide, was localized to cristae, but not to the outer membrane, of hepatic and renal mitochondria. Mitochondria of distal tubule cells showed a stronger reaction. The possible significance of nucleoid-bearing peroxisomes in the developing chick is discussed in terms of nitrogen metabolism, uric acid excretion and the presence of the uricolytic enzymes. The nature of the DAB reaction in peroxisomes and in mitochondria is considered.