Endocytosis of cationized horseradish peroxidase by glomerular epithelial cells is reduced in puromycin glomerulopathy.

Rats were treated with a single intravenous injection of aminonucleoside of puromycin and were sacrificed between 1 and 21 days after injection. The conjugate of horseradish peroxidase with a poly-L-lysine (HRP.PL) was used to reveal endocytotic activity in glomerular epithelial cells (GEC). This conjugate was injected intravenously 2 h before each sacrifice. Renal tissue was taken and treated cytochemically with a conventional DAB technique and observed by light and electron microscopy. The assessment of endocytosis by glomerular epithelial cells was performed on 1-micron sections by counting HRP.PL grains in the GEC and expressing this in terms of the area of glomerulus examined. The results were compared to those found in normal rats. Our results show that GEC endocytotic function was reduced during the whole period of the experiment. It fell quickly from 1 day after puromycin injection and reached the most marked reduction on the 4th day, preceding the peak of proteinuria which was between 7 and 12 days. From the 5th day onward the endocytotic function gradually recovered, but was still abnormal at the end of the experiment.