Effect of beta-D-xyloside on the renal glomerular cells. II. Morphological studies

The effect of p-nitrophenyl-beta-D-xylopyranoside on the renal glomerulus was studied. Rat kidneys were labeled with [35S]sulfate in the presence or absence of beta-xyloside by using an isolated organ perfusion system and were processed subsequently for morphological studies. By using electron microscopy, preferential intracytoplasmic vesiculation of the visceral epithelium was observed in the beta-xyloside-treated kidneys. The vesicles were distributed throughout the cytoplasm, particularly in the vicinity of Golgi apparatus. They were acid-phosphatase negative, devoid of clathrin-coat, and contained osmium-impregnated reaction products. The visceral epithelial foot processes remained firmly attached to the glomerular basement membrane. No loss of cell-surface associated sialoglycoproteins, as evidenced by colloidal iron staining, was observed. No significant change in the morphological features of glomerular endothelial or mesangial cells was noted. By using electron microscopy autoradiography, a significant increase in the number of silver grains over the epithelium, and a decrease in the number over the extracellular matrices was observed. The majority of the grains were either associated with intracytoplasmic vesicles or Golgi apparatus. The mean grain densities (concentration of radiation) increased by 3.6-fold for the epithelium, and decreased by 2.4- and 1.6-fold for the basement membrane and mesangial matrix, respectively. The grain densities over the endothelial and mesangial cells were similar in control and experimental groups. These data indicate that xyloside induces selective alterations in Golgi apparatus of the visceral epithelium and a dramatic imbalance in the de novo synthesized sulfated macromolecules of cellular and extracellular compartments.