Uptake of circulating hyaluronic acid by the rat liver. Cellular localization in situ

The uptake of [3H]acetyl-labelled hyaluronic acid (HA) was examined in the liver, spleen and kidney of the rat after i.v. injection. 3H-activity was located by light- and electron-microscopic autoradiography after measurement by scintillation counting of tissue digests. In the liver, approximately 90% of the radioactivity was located in the sinusoidal endothelial cells, with autoradiographic grains distributed throughout the cytoplasm; 50% of the grains overlay vacuoles 0.3 to 1.2 micron in diameter. A few grains (4%) were located in Disse's space or nearby in the cytoplasm of hepatocytes. No grains were found in Kupffer cells. The remainder were randomly scattered across the sections in a pattern indicating nonspecific background activity. These observations are in accordance with the selective uptake of HA exhibited by dissociated liver cells in vitro. HA concentrations in the spleen and kidney were too low for detection by autoradiography. Splenic concentrations were much lower than in rabbits or mice; in this respect the uptake of circulating HA in the rat resembles that reported for chondroitin 4-sulphate.