Natriuretic peptide production in hypertensive rats with or without cardiac hypertrophy

Cardiac natriuretic peptide (NP=ANF and BNP) production was studied in the aortic banded hypertensive rat after prevention or reversal of cardiac hypertrophy by treatment with low (10 μg/kg) or high (1mg/kg) dose Ramipril. Treatments started at the beginning or after 6 wks of aortic banding and lasted 6 wks. In aortic banded, non treated rats, blood pressure, heart weight (HW)/body weight (BW) ratio, left and right ventricular (LV, RV) βMHC mRNA levels, NP mRNA levels (LV), NP content (LV) and plasma NP were significantly higher than those in sham operated rats. In both the regression and prevention experiments, atrial MHC isoform was α and did not change nor did NP mRNA levels or NP content. In high dose Ramipril treatment rats all parameters were similar to sham operated rats. The low dose Ramipril treatment rats were hypertensive but HW/BW ratio was normal. βMHC mRNA levels remained at the same levels that of aortic banded, non treated rats. NP mRNA levels and NP content (LV) and NP plasma concentration were partially higher than controls but lower than banded animals. It is concluded that: 1. High dose Ramipril treatment normalizes ventricular NP production but regression or prevention of hypertrophy alone (Low dose Ramipril treatment) only partly does so suggesting a relationship to both BP and hypertrophy. 2. ACE inhibition does not affect atrial NP production. 3. Low dose Ramipril treatment reverses anatomical hypertrophy but does not revert the increased βMHC expression suggesting that these are independently regulated processes.