The authors investigated dynamic changes and the interaction of the plasma renin activity (PRA), plasma aldosterone (PAC), i.e. the main representatives of sodium retaining systems, and of the atrial natriuretic factor (ANF) the decisive natriuretic substance in acute expansion of the extracellular volume (ECV) by infusion of two litres of saline in six controls, seven patients with essential hypertension and liver cirrhosis without ascites (6 patients) and with ascites (6 patients). The expansion evoked controversial changes of these systems. It led to a rise of ANF and suppression of PAC and PRA. Although ANF rose after infusion to the roughly similar range (12.4 to 15.7 pmol/l), the natriuretic response to expansion differed significantly in different groups of patients. It was most marked in hypertonic subjects (517.2 to 93.2 mumols/min) and practically zero in ascitic liver cirrhosis (54.2 +/- 44.2 mumols/min). The explanation of this finding may be the persistence of high activity of the renin-angiotensin-aldosterone system despite its partial inhibition by infusion of saline in cirrhosis of the liver (PRA 1.69 +/- 0.66 nmols/l/hr., PAC 1.12 nmol/l). For the renal response to acute expansion of the ECV thus not only the absolute plasma concentration of ANF is decisive but also its ratio to the activity of the sodium retaining renin-angiotensin-aldosterone system.

Keywords: Aldosterone /blood/; Ascites /blood/; Atrial Natriuretic Factor /blood/; Extracellular Space /physiology/; Humans; Hypertension /blood/; Kidney /physiopathology/; Liver Cirrhosis /blood/; Renin /blood/