Localization of urinary procoagulant in the human kidney

By the indirect immunofluorescent and immunoenzymatic techniques with monospecific antiserum against urinary procoagulant (a tissue factor which accelerates blood coagulation), we found the urinary procoagulant in the kidney distributed to the loop of Henle and distal convoluted tubules. In these areas urinary procoagulant was found in association with the luminal and intercellular borders as well as in the cytoplasm of epithelial cells. Both the descending and ascending limbs of Henle were equally stained. The cytoplasmic staining was patchy in distribution among cells of distal tubules and was predominantly localized in the supranuclear areas. Glomeruli, the proximal tubular cells, the vascular wall, and the interstitium were not stained. There was, however, fluorescent staining along the epithelial layers of the Bowman's capsule, which was observed only in the frozen sections. Casts in the distal tubules were also positively stained. These findings suggest that urinary procoagulant is synthesized in the epithelial cells of these particular parts of nephron and is secreted into urine, although its physiologic roles and pathologic significance are not entirely known.