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Brain natriuretic peptide (BNP 1-32) plays an important physiologic role in cardiorenal homeostasis. Recently, it has been reported that BNP 1-32 is rapidly cleaved by the ubiquitous enzyme dipeptidyl peptidase IV to BNP 3-32, which lacks the two NH2-terminal amino acids of BNP 1-32. The bioactivity of BNP 3-32 in cardiorenal regulation is unknown. We hypothesized that BNP 3-32 has reduced vasodilating and natriuretic bioactivity compared with BNP 1-32 in vivo. Synthetic human BNP 3-32 and BNP 1-32 were administered to eight anesthetized normal canines. After baseline measurements, BNP 1-32 at 30 ng x kg(-1) x min(-1) was administered, followed by a washout, a postinfusion clearance, and a clearance with an equimolar dose of BNP 3-32. In four studies, the sequence of BNP 1-32 and BNP 3-32 infusion was reversed. Peptides were compared by analyzing the changes from the respective preinfusion clearance to the respective infusion clearance. *P< 0.05 between peptides. BNP 3-32, unlike BNP 1-32, did not decrease mean arterial pressure (0 +/- 1 vs. -7 +/- 2* mmHg, respectively) and did not increase renal blood flow (+12 +/- 10 vs. +52 +/- 10* ml/min). Effects on heart rate and cardiac output were similar. Urinary sodium excretion increased 128 +/- 18 microeq/min with BNP 3-32 and 338 +/- 40* microeq/min with BNP 1-32. Urine flow increased 1.1 +/- 0.2 ml/min with BNP 3-32 and 2.8 +/- 0.4* ml/min with BNP 1-32. Plasma BNP immunoreactivity was lower with BNP 3-32, suggesting accelerated degradation. In this study, BNP 3-32 showed reduced natriuresis and diuresis and a lack of vasodilating actions compared with BNP 1-32.

Background-BAY 41-2272 is a recently introduced novel orally available agent that directly stimulates soluble guanylate cyclase (sGC) and sensitizes it to its physiological stimulator, nitric oxide. To date, its therapeutic actions in congestive heart failure (CHF) remain undefined. We characterized the cardiorenal actions of intravenous BAY 41-2272 in a canine model of CHF and compared it to nitroglycerin (NTG). Methods and Results-CHF was induced by rapid ventricular pacing for 10 days. Cardiorenal and humoral function were assessed at baseline and with administration of 2 doses of BAY 41-2272 (2 and 10 g · kg Ϫ1 · min Ϫ1 ; nϭ8) or NTG (1 and 5 g · kg Ϫ1 · min

In heart failure (HF), the cardiac hormone natriuretic peptides (NPs) atrial (ANP), B-type (BNP), and C-type (CNP) play a key role to protect cardiac remodeling. The proprotein convertases corin and furin process their respective pro-NPs into active NPs. Here we define in a canine model of HF furin and corin gene and protein expression in normal and failing left atrium (LA) or ventricle (LV) testing the hypothesis that the NP proproteins convertases production is altered in experimental HF. Experimental canine HF was produced by rapid right ventricular pacing for 10 days. NPs, furin, and corin mRNA expression were determined by quantitative RT-PCR. Protein concentration or expression was determined by immunostaining, radioimmunoassay, or Western blot. Furin and corin proteins were present in normal canine LA and LV myocardium and vasculature and in smooth muscle cells. In normal canines, expression of NPs was dominant in the atrium compared with the ventricle. In experimental early stage HF characterized with marked atrial fibrosis, ANP, BNP, and CNP mRNA, and protein concentrations were higher in HF LA but not HF LV compared with normals. In LA, corin mRNA and protein expressions in HF were lower, whereas furin mRNA and protein expressions were higher than normals. NPs and furin expressions were augmented in the atrium in experimental early stage HF and, conversely, corin mRNA and protein expressions were decreased with atrial remodeling. Selective changes of these NP convertases may have significance in the regulation of pro-NP processing and atrial remodeling in early stage HF.