Different regulation of left ventricular ANP, BNP and adrenomedullin mRNA in the two-kidney, one-clip model of renovascular hypertension.

The aim of our study was to clarify whether atrial (ANP) and brain (BNP) natriuretic peptides and the hypotensive peptide adrenomedullin (ADM) are regulated differently in the rat heart in the two-kidney, one-clip model of renovascular hypertension. We assessed messenger ribonucleic acid (mRNA) abundance and distribution of ANP, BNP and ADM in the ventricles and atria of rats after unilateral renal artery stenosis (clipping). Rats were clipped for 6 h or 1, 2 or 4 days and mRNA levels were assessed semiquantitatively in left and right atria and ventricles by RNase protection assay. Left ventricular BNP mRNA up-regulation (4.3-fold after 6 hours) preceded ANP up-regulation (4.5-fold after 1 day) and seemed to be transient, whereas ANP mRNA levels were still elevated at day 4 (2.4-fold vs. sham). The right ventricle and the atria did not participate in these responses. Despite the massive changes of natriuretic peptide mRNAs, ADM mRNA did not change in either the ventricles or the atria. In contrast to ANP and BNP mRNA, which predominate in atrial tissue, mRNA for adrenomedullin is equally distributed in ventricles and atria. Plasma levels of immunoreactive (ir)-ANP and ir-BNP changed in parallel with left ventricular mRNA levels. Our findings suggest that renovascular hypertension induced by clipping the renal artery leads to immediate, but independent, up-regulation of ANP and BNP mRNA in the left ventricle whereas adrenomedullin mRNA is not changed.