Endogenous alpha-atrial natriuretic peptide (ANP) in plasma is elevated in 
various hypervolaemic conditions. Possible relationships between circulating 
immunoreactive ANP and cardiovascular and splanchnic haemodynamics were 
therefore studied in patients with cirrhosis (n = 16) and controls (n = 12). 
Arterial plasma concentration of ANP in supine patients was (mean +/- SEM) 33 
+/- 4 vs 41 +/- 10 pg/ml (9.9 +/- 1.2 vs 12.3 +/- 3.0 fmol/l) in controls 
(n.s.), and there was a weak direct correlation with right atrial pressure (r = 
0.36, P = 0.05). There was no relationship with the presence of ascites or 
diuretic treatment. Central blood volume (CBV, i.e. the blood volume in the 
heart cavities, lungs, and aorta), determined from the mean transit time of 
125I-labelled of 125I-labelled albumin and cardiac output, was significantly 
reduced in cirrhotics compared to controls (1.45 +/- 0.12 vs. 1.83 +/- 0.10 l, P 
less than 0.02) and inversely correlated with portal pressure (r = 0.42, P less 
than 0.05), whereas total plasma volume was somewhat increased (3.51 +/- 0.2 vs. 
3.19 +/- 0.2, 0.05 less than P less than 0.1). A high arterio-venous extraction 
of ANP was found in the splanchnic system (extraction ratio 0.44 vs 0.28), 
kidney (0.45 vs 0.54), lower limb (0.53 vs 0.40), and forearm (0.27 vs 0.18) in 
patients and controls, respectively (n.s.). Our results suggest that the lack of 
elevation of circulating ANP in cirrhosis, even in the presence of actual fluid 
retention, may be explained by central hypovolaemia in these patients. Turnover 
and degradation of ANP is rapid and normal, as evaluated from the tissue 
extraction ratios.