Plasma Concentration and Urinary Excretion of Arginine-Vasopressin in Primary Aldosteronism during the Fluid Deprivation Tests

Summary

Plasma concentration (P_Avp) and urinary excretion (U_Avp) of arginine-vasopressin were studied in 8 patients with primary aldosteronism (PA) during a 36 hour period of fluid restriction in relation to the disturbances of their maximal renal concentrating capacity. The results in untreated patients suffering from PA were compared with the findings in patients after a successful treatment of PA as well as with the results in 9 control subjects. The reduction of maximal renal concentrating ability in PA before the treatment was accompanied with a high excretion of UAVP and the physiological reaction of P_AVP to dehydration. Together with the shift of the regression line of the dependence of U_OSM on U_AVP to higher values of U_AVP this indicates a decrease of the sensitivity of the nephrons to the sufficiently high concentrations of endogenous AVP. The increase of renal AVP clearance in PA participates in the high urinary excretion of AVP. The disturbance of the renal concentrating ability as well as the changes of urinary AVP in PA are mostly reversible. After the successful treatment of PA and the completion of potassium stores in the body as well as the healing of the kaliopenic nephropathy, the maximal renal concentrating capacity and AVP gradually return to values close or equal to those in healthy subjects.