Expression and distribution of brain natriuretic peptide in human right atria.
OBJECTIVE
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 a 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 atria 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 mRNA of specimens were quantitatively measured by Northern blot analysis and also evaluated by in situ hybridization. In addition, plasma levels of ANP and BNP were measured in the patients.


RESULTS
The BNP immunoreactivity was diffusely seen in RA tissue of patients with mean RA pressure (mRAP) of 5 mm Hg or more, but it was noted only in the subendocardial half of the atria of those with mRAP less than 5 mm Hg. There was a 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 mRNA levels were significantly correlated to each other (r = 0.845, p < 0.0002). Plasma 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 mRNA is augmented in the atria with increased pressure, and distributed predominantly in the subendocardial side. The level of BNP mRNA was well correlated with that of ANP mRNA. Thus, these two genes might be commonly regulated in response to atrial pressure.
Doyama
K
K
Third and Second Department of Internal Medicine, Kyoto University School of Medicine, Japan.
Fukumoto
M
M
Takemura
G
G
Tanaka
M
M
Oda
T
T
Hasegawa
K
K
Inada
T
T
Ohtani
S
S
Fujiwara
T
T
Itoh
H
H
Nakao
K
K
Sasayama
S
S
Fujiwara
H
H
D000368:Aged; D009320:Atrial Natriuretic Factor / Q000097:blood / Q000378:metabolism*; D015152:Blotting, Northern; D005260:Female; D006325:Heart Atria / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D008875:Middle Aged; D020097:Natriuretic Peptide, Brain / Q000097:blood / Q000378:metabolism*; D011863:Radioimmunoassay; D014018:Tissue Distribution
D020097:Natriuretic Peptide, Brain; D009320:Atrial Natriuretic Factor