Expression of B-type natriuretic peptide forms in ischemic human hearts

Background: This study sought to determine pro-B-type natriuretic peptide (proBNP), BNP, N-terminal proBNP (NT-proBNP) and GATA-4 in the same cardiac tissue, the correlation among them, and the influence of ischemic etiology on their levels. Methods: Protein levels were analyzed by Western blot techniques and mRNA expression was quantified by quantitative real-time polymerase chain reaction (RT-PCR) in a total of 33 human samples from ischemic (ICM), and control hearts. Results: Tissue protein level of proBNP is 1.5- and 12-fold higher than BNP or NT-proBNP respectively (p<0.0001), and BNP protein level was 8-fold higher than that of NT-proBNP (p<0.0001) in ICM hearts. Furthermore, proBNP mRNA expression was also increased in ICM (4-fold) compared to control hearts (p<0.05), but there was not a significant increase in GATA-4 mRNA. Then, tissue NP forms showed a high correlation among them (proBNP vs. BNP r=0.74, p<0.0001; proBNP vs. NT-proBNP r=0.43, p=0.03; and BNP vs. NT-proBNP r=0.61, p=0.001, respectively). Furthermore, GATA-4 with proBNP (r=0.536, p=0.007) and BNP (r=0.610, p=0.001) in ischemic samples. Finally, we found that proBNP, BNP, NT-proBNP and GATA-4 were increased in our ICM hearts (by 14%, p=0.004; 46%, p=0.024, 33%, p=0.002, and 49%, p=0.026, respectively) compared with controls. Conclusions: This study shows higher protein level of proBNP in human hearts than of BNP and NT-proBNP, increased proBNP mRNA expression in ICM samples, and a good correlation among tissue natriuretic peptide and GATA-4. Finally, ICM shows a high tissue protein level of proBNP, BNP, NT-proBNP and GATA-4. (C) 2011 Elsevier Ireland Ltd. All rights reserved.