Background: Accumulating evidence suggests that blood clotting occurs in
inflamed glomeruli, although its role in the pathophysiology of glomerulonephritis
remains to be elucidated. To address this issue, a simple and reliable method for
evaluating clotting in glomeruli is necessary. Here, we developed an enzyme-linked
immunosorbent assay (ELISA) for thrombin in urine to evaluate the degree of clotting
activation in diseased glomeruli.
Methods: Monoclonal antibodies against human α-thrombin were raised and
used for sandwich ELISA to measure thrombin. Thrombin was measured in urine samples
from normal volunteers and from patients with glomerulonephritis or disseminated
intravascular coagulation (DIC).
Results: Thrombin antigen was not detected in the urine of healthy
volunteers or of patients with DIC, but was detected in the urine from two-thirds of
glomerulonephritic patients. The average concentration in positive samples was 3.79
µg/L. Urinary thrombin concentrations measured by ELISA
correlated well with thrombin activities measured by hydrolysis of a synthetic
substrate.
Conclusion: We suggest that thrombin antigen in urine measured by ELISA
is not affected by systemic thrombin production in the vessels, and reflects blood
clotting activation in glomerulonephritic lesions. A close relationship between
urinary thrombin and glomerulonephritis indicates a possible involvement of clotting
in disease development, and measurement of urinary thrombin may provide a real-time
marker for monitoring renal diseases.
