The effect of class-specific protease inhibitors on the stabilization of B-type natriuretic peptide in human plasma

Background: B-type natriuretic peptide (BNP) is a cardiac hormone that regulates hemodynamic equilibrium. In the circulation, its activity is controlled by proteolytic factors. Accurate measurement of BNP in a patient's plasma may be affected by degradation due to proteolysis.

Objective: We report on the identification and performance of classes of Protease Inhibitors that stabilize BNP in plasma.

Design and methods: Using the Bayer ADVIA Centaur BNP assay, we measured the effect of arginine, serine and/or specific kallikrein Protease Inhibitors (PIs) on exogenous spiked or endogenous BNP in patient plasma.

Results: Compared to controls without inhibitor, all PIs were capable, to varying degrees, of retarding the rate of proteolytic degradation. The kallikrein-specific inhibitor, D-Phe-Phe-Arg-chloromethylketone (PPACK II) was most effective as a single constituent and was able to eliminate BNP degradation in patient samples for up to 6-10 days when stored at 2-8 degrees C.

Conclusions: The stability of BNP was markedly increased in the presence of kallikrein-specific PPACK II and a broad spectrum of serine PIs. Use of these compounds offers a simple method of extending sample handling and storage of plasma samples containing BNP.