Automated measurement of kidney lysosomes by light microscopy. Influence of cyclosporine treatment.

After staining for acid phosphatase, video images were acquired from 1-micron sections of the kidneys of rats treated with cyclosporine. Automated segmentation of the lysosomes was followed by measurements of their area, number and optical density; tubular area was delineated manually. In addition to small lysosomes, representing more than 80% of the total number, all kidneys contained a second population of larger organelles. Cyclosporine treatment with 50 mg/kg/day for one week and with 25 mg/kg/day for three weeks, but not with 25 mg/kg/day for one week, induced a significant increase of lysosomal area, especially in the larger organelles (+200%). In a few animals, this was accompanied by a reduction in the number of lysosomes, suggesting a fusion of the organelles. Other parameters were not consistently modified by treatment. Cyclosporine treatment also elicited the appearance of fat droplets; however, lysosomes were not enlarged in tubular cells containing fat droplets.