Upregulated neurohumoral factors are associated with left ventricular remodeling and poor prognosis in rats with monocrotaline-induced pulmonary arterial hypertension.
BACKGROUND
Left ventricular remodeling might be involved in the pathophysiology of right ventricular hypertrophy/failure due to pulmonary arterial hypertension (PAH), while the left ventricle is considered not under pressure/volume overload.


RESULTS
Rats with monocrotaline-induced PAH were used in the present study to examine whether upregulated neurohumoral factors may induce left ventricular (LV) remodeling and(/or) contribute to prognosis. Morphological analysis revealed a significant increase in the weight of the free walls of both ventricles and the interventricular septum, indicating biventricular hypertrophy, although systemic blood pressure was not elevated. RNase protection assay demonstrated the activation of a fetal gene program in the cardiac muscle of the left and right ventricular free walls. Similar activation of the fetal gene program was observed in the LV of rats continuously infused with angiotensin (AT) II, although this was not the case for rats infused with isoproterenol. Measured plasma levels of ATII, noradrenaline, and brain natriuretic peptide (BNP) were all significantly elevated in the PAH rats. Furthermore, the plasma BNP level positively correlated with the ratio of heart weight to body weight and the plasma level of ATII. Not right but LV hypertrophy was significantly reduced by treatment with an AT II type 1 receptor blocker, valsartan, whereas the effect of an adrenergic alpha1 and beta1,2 blocker, carvedilol, was borderline. Survival rate in the PAH rats was significantly improved when they were treated with valsartan or carvedilol.


CONCLUSIONS
Upregulated neurohumoral factors seem to play an important role in LV remodeling without mechanical overload, and are associated with impairment of prognosis in rats with PAH.
Usui
Shin-ichi
S
Department of Cardiovascular Medicine, Graduate School of Medicine, University of Tokyo, Japan.
Yao
Atsushi
A
Hatano
Masaru
M
Kohmoto
Osami
O
Takahashi
Toshiyuki
T
Nagai
Ryozo
R
Kinugawa
Koichiro
K
D000804:Angiotensin II / Q000097:blood*; D000818:Animals; D006976:Hypertension, Pulmonary / Q000097:blood* / Q000139:chemically induced; D017379:Hypertrophy, Left Ventricular / Q000097:blood / Q000139:chemically induced; D008297:Male; D016686:Monocrotaline / Q000494:pharmacology / Q000633:toxicity*; D020097:Natriuretic Peptide, Brain / Q000097:blood*; D009638:Norepinephrine / Q000097:blood*; D011379:Prognosis; D051381:Rats; D017208:Rats, Wistar; D015854:Up-Regulation / Q000187:drug effects*; D020257:Ventricular Remodeling / Q000187:drug effects*
D000804:Angiotensin II; D020097:Natriuretic Peptide, Brain; D016686:Monocrotaline; D009638:Norepinephrine