Expression and distribution of brain natriuretic peptide in human right atri

Objectives. We investigated expression of brain natriuretic peptide (BNP) as well as atrial natriuretic peptide (ANP) and their genes in human right atria. Their relations with atrial pressure were also examined. Background. The BNP plays roll in electrolyte-fluid homeostasis such as ANP. The tissue level is reported to be elevated in the failing ventricles. However, expression and transmural distribution of BNP in the atri remain unclear. Methods. Expression of ANP and BNP was immunohistochemically investigated in the right atrial (RA) specimens from 21 patients who had undergone cardiac surgery. The mRN of specimens were quantitatively measured by Northern blot analysis and also evaluated by in situ hybridization. In addition, plasm levels of ANP and BNP were measured in the patients. Results. The BNP immunoreactivity was diffusely seen in R tissue of patients with mean R pressure (mRAP) of 5 mm Hg or more, but it was noted only in the subendocardial half of the atri of those with mRAP less than 5 mm Hg. There was significant correlation between the incidence of BNP-positive myocytes and mRAP (r = 0.850, p < 0.0001). Conversely, ANP-positive myocytes were found diffusely in all cases. In Northern blot analysis, the mRNAs levels of ANP and BNP in the atrial tissue were positively correlated with the mRAP (ANP, p = 0.775, p < 0.005 and BNP, p = 0.771, p < 0.005). In situ hybridization confirmed these findings. The mRN levels were significantly correlated to each other (r = 0.845, p < 0.0002). Plasm ANP and BNP levels were elevated in the patients compared with that in controls; however, none were significantly correlated with the mRAP. Conclusions. Expression of BNP and BNP mRN is augmented in the atri with increased pressure, and distributed predominantly in the subendocardial side. The level of BNP mRN was well correlated with that of ANP mRNA. Thus, these two genes might be commonly regulated in response to atrial pressure.