The circulatory model in metabolic studies of rapidly renewed hormones: application to anp kinetics. Pilo, A., G. Iervasi, A. Clerico, F. Vitek, S. Berti, C. Palmieri, A. Biagini, L. Donato. Laboratory of Cardiovascular Endocrinology, CNR Institute of Clinical Physiology, Pisa, Italy, Institute of Biophysics, First Medical Faculty, Charles University, Prague, Czech Republic.
APStracts 4:0260E, 1997.
In an attempt to identify and quantify the sites of Atrial Natriuretic Peptide (ANP) degradation, a new tracer experiment has been developed. [125I]ANP was injected as a bolus just upstream from the right atrium, and blood was sampled from two different sites (pulmonary artery and aorta) in eight cardiac patients. Data analysis was carried out using a physiologically based circulatory model consisting of three blocks in series (right heart, lungs and left heart, and periphery) supplied by the same flow (cardiac ouput, measured by thermodilution); the extraction coefficients of the three blocks and of whole body could be determined from the areas under tracer concentration curves in plasma (AUCs). The values of AUCs (mean+/-SD) were: 64.8+/-9.4 and 65.5+/-10.7% dose/L min for pulmonary curve and aorta curve, respectively; the area under the pulmonary curve could be subdivided into area under first pass curve (30.6+/-4.7% dose/L min) and area under recirculating curve (34.0+/ -7.7% dose/L min). The MCR of [125I]ANP - computed as dose/AUC of the recirculating curve - was 3.1+/-0.7 L/min and the whole body extraction was 47.6+/-6.6%. In our patients with myocardial dysfunction neither right heart block nor lungs and left heart block significantly extracted ANP, and the periphery block accounted for almost all removal of the hormone from the blood. 

Received 5 March 1997; accepted in final form 13 November 1997.
APS Manuscript Number E100-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 12 December 1997