Abstract
Using a tracer method, we evaluated, in vivo, the main turnover parameters and the main metabolic pathways of ANP in 10 normal subjects. HPLC was used to purify the labeled hormone and the principal labeled metabolites present in venous plasma samples collected at determined times after tracer injection. The main ANP kinetic parameters were derived from the disappearance curves of [125I] ANP, which were satisfactorily fitted by a biexponential function in all subjects. Newly produced ANP initially distributes in a large, plasma equivalent space (10.9±3.6 l/m2 body surface); the hormone rapidly leaves this space due to both degradation and to distribution in peripheral spaces. The mean residence time in the body (19.4±19.8 min) and the plasma equivalent total distribution volume (28.2±11.5 l/m2) indicate that ANP is also widely distributed outside the initial space in humans (circulating ANP is no more than 1/15 of the body pool). Metabolic clearance rate values were distributed across a wide range (from 740 ml/min/m2 to 2581 ml/min/m2, mean 1849 ml/min/m2), and were shown to strongly correlate (R=0.962) with the daily urinary excretion of sodium. A complete separation of labeled ANP from its labeled metabolites was achieved by the HPLC technique; at least 3 different peaks due to labeled metabolites in vivo produced from the injected [125I]ANP1–28 were found. The first Chromatographic peak eluted showed an identical elution time to monoiodotyrosine. At least two other peaks due to in vivo generated labeled metabolites were well identified in the chromatograms: one peak (coeluting with labeled COOH-terminal tripeptide, H-Phe-Arg-Tyr-OH) was eluted ahead and one (coeluting with labeled peptide fragments ANP7–28, ANP13–28, and ANP18–28) behind the elution peak of the labeled ANP. The peak of labeled tyrosine appearing in the plasma ranged between 3 and 5 min after tracer injection; the other two peaks of radioiodinated metabolites showed their highest activity in the first sample (1.5 min), suggesting an earlier occurrence of their peaks. These labeled metabolites seem to be intermediate peptides, between the intact circulating form of the hormone and the final labeled metabolite (tyrosine), which is the last amino acid of the peptide hormone, produced in vivo after injection of the tracer. In conclusion, our kinetic data indicate that: 1) newly produced ANP is rapidly distributed and degraded; 2) the body pool of the hormone can be considered a combination of two exchanging spaces, circulating ANP representing no more than 1/15 of the body pool; 3) MCR of ANP is closely related to sodium intake; 4) labeled tyrosine is the main endogenous metabolite of the hormone in humans; 5) both receptor-mediated and enzymatic degradation play an important role in the turnover of ANP in humans.
Similar content being viewed by others
References
De Bold A.J. Atrial natriuretic factor: a hormone produced by the heart. Science 230: 767, 1985.
Goetz K.L. Physiology and pathophysiology of atrial peptides. Am. J. Physiol. 254: E1, 1988.
Atlas S.A., Laragh J.H. Atrial nauriuretic factors and its involvement in hypertensive disorders. In: Laragh J.H., Brenner B.H. (Eds), Hypertension pathophysiology, diagnosis and management. Raven Press Ltd, 1990, New York, p. 861.
Condra C.L., Leldy E.A., Bunting P., Colton CD., Nutt R.F. Clearance and early hydrolysis of Atrial Nautriretic Factor in vivo. Structural analysis of cleavage sites and design of an analogue that inhibits hormone cleavage. J. Clin. Invest. 81: 1348, 1988.
Sonnenberg J.L., Sakane Y., Jeng A.Y., Koehn J.A., Ansell J.A., Wennogle L.P., Ghai R.D. Identification of protease 3.4.24.11 as the major Atrial Natriuretic Factor degrading enzyme in the rat kidney. Peptides 9: 173, 1988.
Ruskoaho H. Atrial natriuretic peptide: synthesis, release, and metabolism. Pharmacol. Rev. 44: 479, 1992.
Tan A.C., Russel F.G., Thien T., Benraad T.J. Atrial natriuretic peptide. An overview of clinical pharmacology and pharmacokinetics. Clin. Pharmacokint. 24: 28, 1993.
Iervasi G., Clerico A., Berti S., Pilo A., Vitek F., Biagini A., Baratto M.T., Bianchi R., Donato L. ANP kinetics in normal men: in vivo measurement by a tracer method and correlation with sodium intake. Am. J. Physiol. 264: F480, 1993.
Clerico A., Del Chicca M.G., Giganti M., Zucchelli G.C., Piffanelli A. Evaluation and comparison of the analytical performances of two RIA kits for the assay of artrial natriuretic peptides (ANP). J. Nucl. Med. Allied Sci. 34: 81, 1990.
Clerico A., Opocher G., Pelizzola D., Panzali A.F., Andreone P., Del Chicca M.G., Giganti M., Zucchelli G.C., Mantero F., Albertini A., Piffanelli A. Evaluation of the analytical performance of RIA methods for measurement of Atrial Natriuretic Peptides (ANP): a multicentre study. J. Clin. Immunoassay 14: 251, 1991.
Maack T. Receptors of atrial nautriuretic factors. Annu. Rev. Physiol. 54: 11, 1992.
Hirata Y., Tomita M., Takada S., Yoshimi H. Vascular receptor binding activities and cyclic GMP responses by synthetic human and rat atrial natriuretic peptides (ANP) and receptor down-regulation by ANP. Biochem. Biophys. Res. Commun. 128: 538, 1985.
Cuneo R.C., Espiner E.A., Nicholls M.G., Yandle T.G., Joyce ST., Gilchrist N.L. Renal, hemodynamic, and hormonal responses to atrial nautrietic peptides infusions in normal man, and effect of sodium intake. J. Clin. Endocrinol. Metab. 63: 946, 1986.
Guaquelin G., Garcia R., Carrier F., Cantin M., Gutkowaska J., Thibault G., Schiffrin E.L. Glomerular ANF receptor regulation during changes in sodium and water matabolism. Am. J. Physiol. 254: F51, 1988.
Katafuchi T., Mizuno T., Hagiwara H., Itakura M., Ito T., Hirose S. Modification by NaCl of atrial Natriuretic Peptide receptor levels and cyclic GMP responsiveness to Atrial Natriuretic Peptide of cultured vascular endothelial cells. J. Biol. Chem. 267: 7624, 1992.
Murthy K.K., Thibault G., Garcia R., Gutkowska J., Genest J., Cantin M. Degradation of atrial natriuretic factor in the rat. Biochem. J. 240: 461, 1986.
Kenny A.J., Stephenson S.L. Role of endopeptidase-24.11 in the inactivation of atrial natriuretic peptide. FEBS Lett. 232: 1, 1988.
Vanneste Y., Pauwels S., Lambotte L., Michel A., Dimaline R., Deschodt L.M. Respective roles of Kallikrein and endopeptidase 24.11 in the metabolic pathway of atrial natriuretic peptides in the rat. Biochem. J. 269: 801, 1990.
Yandle T., Crozier I., Niclolls G., Espiner E., Carne A., Brennan S. Amino acid sequence of atrial natriuretic peptides in human coronary sinus plasma. Biochem. Byophsy. Res. Commun. 146: 832, 1987.
Sybertz E.J., Chiu P.J.S., Vemulapalli S., Pitts B., Foster C.J., Watkins R.W., Barnett A., Haslanger M.F. SCH 39370, a neutral metalloendopeptidase inhibitor, potentiates biological responses to atrial natriuretic factor and lowers blood pressure in desoxycorticosterone acetate-sodium hypertensive rats J. Pharmacol. Exp. Ther. 250: 624, 1989.
Charles J.C., Espiner E.A., Cameron V.A., Richards A.M., Yandle T.G., Sybertz EJ. Hemodynamic and hormonal effects of neutral endopeptidase inhibitor SCH 39370 in sheep. Hypertension 17: 643, 1991.
Richards M., Espiner E., Frampton C., Ikram H., Yandle T., Sopwith M., Cussans N. Inhibition of endopeptidase EC 24.11 in humans. Renal and endocrine effects. Hypertension 16: 269, 1990.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Clerico, A., Iervasi, G., Berti, S. et al. In vivo measurement of ANP overall turnover and identification of its main metabolic pathways under steady state conditions in humans. J Endocrinol Invest 18, 194–204 (1995). https://doi.org/10.1007/BF03347802
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/BF03347802