Acta Physiol Scand zyxwvutsrq 1987, zyxwvut 131, 265-272 zyxwvu Central venous pressure zyxw - a physiological stimulus for secretion of atrial natriuretic peptide in humans? H. J. SCHUTTEN, A. c. JOHANNESSEN, c. TORP-PEDERSEN, K. SANDER-JENSEN, P. BIE and J. WARBERG Department of Medical Physiology C, Panum Institute, University of Copenhagen, Denmark SCHUTTEN, H. J., JOHANNESSEN, A. C., TORP-PEDERSEN, C., SANDER-JENSEN K., BIE, P. & WARBERG, J. 1987. Central venous pressure - a physiological stimulus for secretion of atrial natriuretic peptide in humans? Acta Physiol Scand 131, 265-272. Received 17 December 1986, accepted zyxwvu 22 April 1987. ISSN 0001-6772. Department of Medical Physiology C, Panum Institute, Copenhagen, Denmark. A sensitive radio-immunoassay (RIA) for the measurement of human a-atrial natriuretic peptide (ANP) in extracted plasma was developed and used in a study of the possible effect of posture on the concentration of ANP in plasma. The least detectable quantity was less than 2 pg per tube equivalent to 5 pg ml-' plasma. In the middle sensitivity range (approximately 50 pg per tube), the within-assay and between-assay coefficients of variation were 4.0 and 2.8%, respectively. The recovery of ANP added to plasma prior to extraction was 95-101 yo. High pressure liquid chromatography (HPLC) of plasma extracts revealed that endogeneous ANP was eluted in the same fractions as synthetic ANP. In order to investigate the effect of posture on the concentration of ANP in plasma six healthy volunteers were exposed to five positions in the following sequence: supine, standing, sitting, supine and roo head-down tilt on a tilt-table. The concentration of ANP was lower in the standing and sitting position than in the supine and head-down tilted position. In another study six healthy volunteers were subjected to passive tilting on a tilt-table in order to evaluate the effect of tilting on blood pressure (BP), heart rate, central venous pressure (CVP) and the concentration of ANP in plasma. It was found that a fall in CVP was accompanied by a significant decrease in the concentration of ANP and that a rise in CVP was accompanied by a rapid increase in the concentration of ANP in plasma. The results are in agreement with the hypothesis that CVP is a physiological stimulus for the secretion of ANP. Key words : atrial natriuretic peptide, central venous pressure, radio-immunoassay. Peptides possessing natriuretic, diuretic and vasorelaxant properties have been isolated from human atrial tissue (a-, zyxwvuts p- and y- human atrial natriuretic peptides), and a gene encoding for a common precursor molecule has been identified (Kangawa et al. 1985, Kangawa & Matsuo 1984, Oikiwa et zyxwvutsrqp al. 1984). Of these, a-human atrial natriuretic peptide (ANP), consisting of 28 amino acids, seems to be the predominant peptide in the circulation (Sugawara et al. 1985, Theiss et al. 1986, Yamaji et al. 1985). Correspondence : H. J. Schutten, MD, Department of Medical Physiology C, 3C Blegdamsvej, Copen- hagen N, DK-2200 Denmark. Infusion of large amounts of synthetic ANP in humans results in a rapid increase in diuresis and natriuresis and a fall in arterial blood pressure (Richards et al. 1985, Tikkanen et al. 1985). The mechanisms by which ANP elicits the natriuretic and diuretic effects on the kidneys seem to be a combination of an increase in glomerular filtra- tion rate and a decrease in reabsorption of sodium in the distal tubules of the nephron (Murray et al. 1985, Zeidel et al. 1986, Sonnenberg 1985, Johannessen et al. 1986, Theiss et al. 1986, Baines et al. 1983). Infusion of isotonic saline in humans results in an increase in the concentration of ANP in 265 zy ACT 131 10