Four experimental groups of rats treated with (1)
DOCA-
salt, (2)
DOCA or (3)
salt, and (4) controls were used to study the participation of
brain natriuretic peptide (BNP) in the development of
hypertension. Plasma and cardiac tissue concentrations of BNP as well as
atrial natriuretic peptide (
ANP) were measured in each group by using radioimmunoassays specific to rat BNP or
ANP. Plasma BNP levels in
DOCA-
salt hypertensive group were higher than those in control (p less than 0.01),
salt (p less than 0.01) and
DOCA (p less than 0.01) groups. A positive correlation was observed between plasma BNP levels and blood pressure (r = 0.70, p less than 0.001) and between plasma
ANP levels and blood pressure (r = 0.62, p less than 0.001). Plasma BNP/
ANP ratio increased parallel with elevation of blood pressure. Plasma BNP levels correlated negatively with atrial BNP concentration (r = -0.33, p less than 0.05), but positively with ventricular BNP (r = 0.76, p less than 0.001). Compared with controls, tissue BNP-45/gamma-BNP ratio in the
DOCA-
salt rats was lower in atrium, but higher in ventricle. Thus, in
DOCA-
salt hypertension atrial BNP decreased with exhaustion of stored
BNP-45, while ventricular BNP increased as
BNP-45 accumulated. These results suggest that BNP is a novel cardiac
hormone, synthesized, processed and secreted in response to changes in blood pressure. BNP may play different roles in controlling blood pressure than those assumed by
ANP.