Radioimmunoassay of atrial natriuretic peptide in human plasma: Application to studies of volume and blood pressure homeostasis

Sensitive radioimmunoassay for determination of immunoreactive atrial natriuretic peptide (ANP) in human plasma was developed and employed for the study of plasma ANP concentrations in healthy controls under basic conditions (2.4±0.1 pmol/l and during volume expansion by saline infusion (9.6±2.0 pmol/l and 14.2±1.8 pmol/l, respectively). Plasma renin activity and plasma aldosterone concentration exhibited opposite changes during saline infusion. In the pathological states associated with extracellular fluid volume (ECFV) expansion, ANP concentration were significantly higher than in the controls (liver cirrhosis 8.6±0.9; congestive heart failure 33.1±4.8; chronic renal failure before hemodialysis 72.2±6.4 pmol/l). Further volume expansion in liver cirrhosis by saline infusion led to further increase in ANP (13.3±1.3 and 16.1±1.5 pmol/l, respectively) and ECFV reduction by ultrafiltration during hemodialysis in chronic renal failure diminished but did not normalize plasma ANP (22.5±2.9 pmol/l). In patients with arterial hypertension the concentration of ANP exceeded the normal range by 62.5% and reached 8.0±0.5 pmol/l on the average. Our results support the suggestion that ANP is an important regulatory humoral mechanism participating in the regulation of sodium, volume and blood presure homeostasis. (author). 2 tabs., 30 refs