Humoral and Renal Response to Acute Volume Loading in Patients with Essential Hypertension

Summary

The effect of acute volume expansion (2 liters of saline solution in 2 h) on plasma concentrations of atrial natriuretic factor (ANF), plasma aldosterone concentration (PAC), plasma renin activity (PRA) and their relationship to the renal excretion of urine, sodium and potassium were studied in 6 control subjects and 7 patients with essential hypertension (EH) WHO stage I. Saline infusion provoked comparable rise in plasma ANF in both groups (from 2.98 ± 0.45 to 12.36 ± 1.74pmol/l in the control subjects and from 3.80 ± 0.72 to 15.78 ± 2.06 pmol/1 in EH patients), significant drop in PRA (from 0.915 ± 0.419 to 0.256 ± 0.127 nmol/l/h in controls and from 1.711 ± 0.324 to 0.714 ± 0.128 nmol/l/h in EH) and in PAC (from 0.30 ± 0.07 to 0.14 ± 0.03 nmol/1 in control subjects and from 0.53 ± 0.13 to 0.24 ± 0.07 nmol/1 in EH). The increase of plasma ANF concentrations after volume expansion might be involved in the suppression of PRA and PAC found after this stimulus. Similar increase in plasma ANF after saline infusion in both groups was associated with significantly greater urine and sodium excretion in EH than in controls. From these results it may be suggested that the acute volume expansion during saline infusion evokes a comparable release of ANF into circulation in both EH patients and controls. In EH patients, however, the similar rise in ANF is accompanied by a more pronounced diuretic and natriuretic response. This exaggerated natriuresis after acute volume and sodium loading cannot be explained solely by a rise in ANF. Its renal effect depends on the interaction with many other haemodynamic, renal and humoral mechanisms — in the humoral area primarily on the functional interaction with the renin-angiotensin-aldosterone system.

Key words

Atrial natriuretic factor - Renin-aldosterone system - Saline infusion - Essential hypertension - Natriuresis