Presence of C-type natriuretic peptide in human kidney and urine

Presence of C-type natriuretic peptide in human kidney and urine. The current study was undertaken to investigate the presence of CNP immunoreactivity in both human kidney and urine. Immunohistochemical staining with an indirect immunoperoxidase method utilizing an antibody which is 100% cross-reactive to both CNP-53 and CNP-22 was performed on five human kidney specimens (three biopsies of normal cadaveric donor kidneys and two of normal autopsy specimens). CNP immunoreactivity was positive in proximal, distal and medullary collecting duct tubular cells in a cytoplasmic and granular staining pattern. CNP immunoreactivity was also determined in the urine of five healthy volunteers utilizing a sensitive and specific double-antibody radioimmunoassay with a mean concentration of 10.8 ± 1.0 pg/ml. With the utilization of high pressure liquid chromatography, this immunoreactivity proved to be consistent with both the low molecular weight form, CNP-22, as well as the high molecular weight form, CNP-53. Urinary excretion of CNP was also measured in normal subjects (N = 5) and in patients with congestive heart failure (CHF, N = 6). CHF patients excreted over three times more CNP than normals (27.2 ± 2.8 vs. 8.7 ± 0.81 pg/min, P < 0.004) despite no difference between the two groups in plasma CNP concentrations (6.97 ± 0.28 vs. 8.08 ± 1.52 pg/ml, P = NS). This study demonstrates for the first time the presence of CNP immunoreactivity in human kidney and suggests that renal tubular cells may be an additional non-vascular site of synthesis for this cardiorenal acting peptide. This study also demonstrates an increase in urinary CNP excretion in congestive heart failure

776-4 Intact cNOS-NO-cGMP Pathway in the Failing Human Heart

Nitric oxide (NO) is a potent endothelium-derived relaxing factor which also may modulate cardiac myocyte inotropism and growth via increases in cGMP. While both the constitutive (cNOS) and inducible (iNOS)forms of nitric oxide synthase have been detected in mammalian hearts, the overall presence and activity of the cNOS-NO-cGMP pathway in the normal and failing human heart remains poorly defined. The present studies were designed to investigate the cNOS-NO-cGMP pathway in normal and failing human atrial and ventricular myocardium and to determine plasma NO and cGMP in the presence and absence of CHF. Myocardial tissue and plasma were obtained from five end-stage heart failure patients undergoing cardiac transplantation and five cardiac donors. Normal plasma NO and cGMP were also determined in normal humans without disease. cNOS production and localization were determined utilizing Northern blot analysis, in situ hybridization and immunohistochemistry with probes for endothelial-NOS and brain-NOS. Plasma and tissue NO were measured by nitrate determination utilizing chemiluminescence. Northern blot analysis and in situ demonstrated cNOS to be present and localized to atrial and ventricular myocytes in equal concentrations and distributions in normal and failing hearts. Tissue NO as determined by nitrate concentration was detectable and equal in normal and failing hearts while plasma NO concentration tended to be increased in CHF patients. Cardiac tissue cGMP paralleled tissue NO, although, plasma cGMP concentration was significantly increased in CHF patients compared with normal subjects. The present studies demonstrate that cNOS mRNA and cNOS protein are present in the normal human heart and this cNOS-NO-cGMP pathway is preserved in the failing human heart. These studies suggest that this paracrine and autocrine pathway may continue to function in the control of myocardial function in the failing human myocardium

Pro–B-Type Natriuretic Peptide1–108 Circulates in the General Community Plasma Determinants and Detection of Left Ventricular Dysfunction

ObjectivesThe purpose of this study was to investigate circulating pro–B-type natriuretic peptide (proBNP1–108) in the general community and evaluate its ability to detect left ventricular (LV) dysfunction.BackgroundThe current concept for cardiac endocrine function is that, in response to cardiac stress, the heart secretes B-type natriuretic peptide (BNP1–32) and amino-terminal pro–B-type natriuretic peptide (NT-proBNP1–76) after intracardiac cleavage of their molecular precursor, proBNP1–108. We hypothesized that proBNP1–108 circulates in normal human subjects and that it is a useful biomarker for LV dysfunction.MethodsOur population-based study included a cohort of 1,939 adults (age ≥45 years) from Olmsted County, Minnesota, with 672 participants defined as healthy. Subjects underwent in-depth clinical characterization, detailed echocardiography, and measurement of proBNP1–108. Independent factors associated with proBNP1–108 and test characteristics for the detection of LV dysfunction were determined.ResultsProBNP1–108 in normal humans was strongly influenced by sex, age, heart rate, and body mass index. The median concentration was 20 ng/l with a mean proBNP1–108 to NT-proBNP1–76 ratio of 0.366, which decreased with heart failure stage. ProBNP1–108 was a sensitive (78.8%) and specific (86.1%) biomarker for detecting LV systolic dysfunction, which was comparable to BNP1–32, but less than NT-proBNP1–76, in several subsets of the population.ConclusionsProBNP1–108 circulates in the majority of healthy humans in the general population and is a sensitive and specific biomarker for the detection of systolic dysfunction. The proBNP1–108 to NT-proBNP1–76 ratio may provide insights into altered proBNP1–108 processing during heart failure progression. Thus, this highly specific assay for proBNP1–108 provides important new insights into the biology of the BNP system