UROKINASE-PLASMINOGEN ACTIVATOR IS SYNTHESIZED IN-VITRO BY HUMAN GLOMERULAR EPITHELIAL-CELLS BUT NOT BY MESANGIAL CELLS

The plasmin protease system may have a role in maintaining the patency of renal tubules and in regulating matrix degradation within the glom erulus. Urokinase-plasminogen activator (u-PA) is a serine protease wh ich plays an important part in the regulation of plasmin production fr om plasminogen. The synthesis of u-PA by cultured human glomerular cel ls, in particular mesangial cells, is controversial. The present study describes the presence of u-PA in supernatants of pure cultures of hu man glomerular epithelial cells (EC), cocultures of EC and human mesan gial cells (MC) and whole glomeruli, but not within pure cultures of M C. To confirm the synthesis of u-PA mRNA in glomerular EC, cocultures of EC and MC were tested by in situ hybridization with u-PA antisense and sense digoxigenin-labeled RNA probes. Cytoplasmic localization of u-PA mRNA was demonstrated only in the EC, thus confirming the absence of synthesis of u-PA by human mesangial cells in culture.