Inhibitors Interfering with the Quantitative Estimation of Tissue Plasminogen Activator

The commonly used quantitative assay for plasminogen activator in tissues by Astrup and Albrechtsen (1957) was re-evaluated with special reference to the presence of inhibitors in tissue extracts at different stages of the procedure.Human lung, liver, and placenta tissues were chosen for their different activator and inhibitor content. Samples of the extracts were tested for inhibitory capacity against purified human tissue plasminogen activator, urokinase, and plasmin on different kinds of fibrin plates.The procedure for preparing the samples according to Astrup and Albrechtsen did not completely eliminate the inhibitory action against the plasminogen activators added. The presence of inhibitors was partly obscured by 2M KCNS in the sample. In order to quantitate the plasminogen activator content in tissues, the method should be revised with respect to the elimination of inhibiting material.Some interesting aspects of the inhibitory components extracted from liver and placenta were revealed by comparing urokinase inhibition to tissue activator inhibition as to the degree of denaturation during the procedure. It was suggested that, although they have much in common, urokinase and tissue activator inhibitors are separate entities.