Antithrombin III in children with various renal diseases.

Levels of antithrombin III (AT-III) activity and antigen in plasma and urine in children with renal diseases, and their correlation with the light microscopic findings of kidney tissue and the fluorescence of glomeruli, were investigated. AT-III activity in plasma was reduced slightly during the acute stage of acute glomerulonephritis and moderately in the relapse stage of nephrotic syndrome, whereas a small increase of AT-III antigen level in urine was noted in the acute stage of glomerulonephritis and considerably more was observed during the relapse stage of nephrotic syndrome. During the acute stage of glomerulonephritis or in some primary persistent glomerulonephritis (IgA nephritis, non-IgA nephritis), Henoch-Schönlein purpura nephritis and nephrotic syndrome, localization of small amounts of AT-III was noted on the capillary walls of glomeruli. These findings were in parallel with the proliferative changes of glomeruli. However, the AT-III localization did not change in parallel with the light microscopic findings or degree of the fluorescence of the fibrinogen/fibrin-related antigen. It was thought that the existence of AT-III antigen on the capillary walls of the glomeruli might be associated with the inhibition of excessive fibrin formation by AT-III.