Effects of dextran-containing perfusion fixatives on intraluminal compounds in rat kidney tubules

In the present study on rat kidney tubules an intraluminal, electron-dense granular substance was found in animals perfusion-fixed with dextran-containing fluids. Most findings were made in thick ascending limbs of Henle and distal convoluted tubules. The incidence decreased from 50% to zero when intravascular rinsing time was increased from zero to 70 sec. In animals fixed without dextran no such substance was found. In some thick ascending limbs of Henle and distal convoluted tubules a similar electron-dense substance was found along the apical plasmalemma of some cells. The origin of the observed substances is at present not defined, but may represent a coprecipitation of dextran and (glyco)proteins caused by glutaraldehyde.