Observations on the segmentation of the proximal tubule in the rat kidney: Comparison of results from phase contrast, fluorescence and electron microscopy

Abstract

The segmentation of the proximal tubule in the normal rat kidney was studied by phase contrast, fluorescence and electron microscopy. Three different segments were observed with all methods. The first segment comprised the beginning of the convoluted part of the proximal tubule, the second segment included the end of the convoluted and the beginning of the descending part of the proximal tubule, and the remaining portion of the descending part formed the third segment. Pronounced differences were present between cells in the three segments with respect to size and frequency of occurrence of acid phosphatase containing cytoplasmic bodies, length of brush border projections, size and arrangement of mitochondria, and extent to which the proximal tubule cells interdigitated. Characteristic differences were also observed between proximal tubules from male and female rats.