PreproBNP is composed of 134 amino acid residues (a.a.r.) and is synthesized in cardiac myocytes. Removal of signal peptide results in the appearance of proBNP molecule. Then proBNP is cleaved by unknown protease forming two peptides; BNP and N-terminal part of the proBNP. Both BNP (biologically active molecule) and NT-proBNP (physiological activity is not clarified) as well as unprocessed proBNP are secreted into the bloodstream and circulate in human blood.
It was established that proBNP synthesis increases in response to mechanic or neurohormonal stimulation of the heart that leads to the increase of BNP and NT-proBNP concentrations in blood. Elevated level of BNP and NT-proBNP is described for patients with different cardiovascular pathologies: heart failure (HF), left ventricular dysfunction, unstable angina and myocardial infarction. Blood concentration of both analytes in HF patients correlates with the severity of disease. It has been reported that peptides concentrations are already elevated in asymptomatic patients during the very early stage of heart failure (NYHA I stage according to the New York Heart Association classification). Cardiac patients with symptoms of severe HF (NYHA class III or IV) and myocardial dysfunction show significantly increased values of BNP. Therefore BNP and NT-proBNP measurements in human blood are used for evaluation of patients with suspected HF and assessment of severity of the disease.
BNP and NT-proBNP measurements are also useful for risk stratification of the patients with different cardiac pathologies. It was demonstrated that patients with possible complications are characterized by significantly higher BNP and NT-proBNP concentrations than patients without complications. At present both analytes are used in clinical practice and still there is no agreement between clinicians which one is preferable. There is a correlation between NT-proBNP and BNP concentrations and apparently their diagnostic and prognostic values are similar.
Recently obtained new data that could significantly influence the current approach to both BNP and NT-proBNP measurements. First of all, it was shown that the central parts of NT-proBNP and proBNP molecules circulating in human blood are glycosylated. Schellenberger et al. also reported that recombinant proBNP in CHO cells is expressed as a glycoprotein. Several sites of glycosylation located in the central part of the molecule were documented for the recombinant proBNP expressed in the CHO cells. It was demonstrated also that proBNP in patients’ blood is glycosylated too. Advanced ImmunoChemical specialists have shown that polysaccharide residues prevent antibodies from interaction with some regions of endogenous NT-proBNP and proBNP molecules. We have also demonstrated that the degree of glycosylation varies from patient to patient significantly and in the case of the high level of glycosylation concentrations of NT-proBNP and proBNP in human blood can be seriously underestimated. Thus antibodies that are specific to the regions not affected by glycosylation should be selected for the development of proBNP and NT-proBNP immunoassays.
Scientists demonstrated recently that proBNP is the major BNP-immunoreactive form in human blood. In other words BNP assays detect mostly proBNP in human blood samples. The ratio proBNP/BNP is not constant and varies from patient to patient. We suggested that proBNP measurements by assays, utilizing one antibody specific to the BNP and another to the NT-proBNP part of the molecule, might be of the same clinical value as BNP measurements.
Advanced ImmunoChemical offers a set of high-affinity monoclonal an¬tibodies, specific to different epitopes of BNP and NT-proBNP molecules. We also supply our customers with detailed additional information about different applications.
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