Summary. Urinary trypsin inhibitors (TI) were differentiated by the electrophoretic
fractionation as well as by selective inactivation by heating, acidification, acetone
and chloroform respectively. The labile TI has been found in urine of patients with
nephrotic syndrome. It moves with α(1)-globulin fraction and its excretion corresponds
to the degree of proteinuria. The urinary excretion of the stable, PCIA-soluble TI in
renal diseases does not depend on the degree of proteinuria. The highest levels of
this inhibitor may be observed in renal insufficiency. It moves with albumins. The
same electrophoretic mobility has the inhibitor found in urine in various other
diseases (acute inflammations, cancer, obstructive jaundice) and in healthy persons.
In some cases two electrophoretic fractions of the stable TI have been found : the
fast and the slow one, moving with albumins and β-γ-globulins resp., but there is not
ultimate proof, that they are separate entities. The protein precipitation by PC1A is
a simple, good method for isolation of the stable, PCIA-soluble inhibitor from others
filtrated to urine in patients with proteinuria.