Assay of Plasmin and Plasminogen Activity in Plasma Using a Detergent Having a Long Alkyl Chain

The inhibitory effect of α2-plasmin inhibitor (α2PI) on plasmin (PLN) was found to be cancelled by a detergent having a long normal alkyl chain. Since the detergent did not affect the PLN activity, it should be useful for the determination of plasminogen (PLG) and PLN in plasma that contains a considerable amount of α2PI. PLN generation from PLG by urokinase (UK) was not inhibited by plasma α2PI when cetyltrimethylammonium bromide (C16Me3Br) was added into the reaction media. 16Me3Br (0.015%) cancelled the effect of at least 5μg/ml of α2PI in the sample solution. This concentration corresponds to 200μg/ml in plasma before dilution and it is about three times the α2PI level in normal plasma. The standard curve of the PLG-UK system gave the linearity from 0 to at least 400μg/ml of PLG in plasma before dilution. This concentration is as twice the level in normal plasma. Accordingly, plasma PLG can be correctly determined by using this detergent for the reagent.