Quarterly Journal of Microscopical Science, Vol s3-95, 23-31, Copyright © 1954 by Company of Biologists

Histological and Polarization Studies of the Brush Border of the Proximal Convoluted Tubules of the Rat Kidney

¹ Department of Experimental Pathology, University of Birmingham

The kidneys of rats were examined histologically after the intraperitoneal injection of haemoglobin and also after the intrarenal injection of a graphite suspension. During haemoglobin excretion spaces can be seen running across the brush border of the proximal convoluted tubules. These spaces are filled by the reabsorbed haemoglobin passing from the tubular lumen into the tubular cells. After intratubular injection of a graphite suspension, particles about 0.5 µ diameter cross the border and appear in the cell cytoplasm.

Examination with the polarizing microscope shows the brush border to have positive form and negative intrinsic birefringence with respect to the length of the striations.

These findings are considered in relation to the appearances found on electron microscopy. It is suggested that on present evidence it is most likely that the brush border consists of rodlets of the order of 300-600 Å diameter, with an orientated molecular structure at right angles to their length. These rodlets are gathered in tufts so that they diverge from one another. The spaces between the tufts at their bases is about 0.3-0.5 µ. and at their tips they just touch one another.