Renal clearance studies were performed during anti-diuresis (before and after hypertonic saline infusion) and during water diuresis in three hypertensive patients with normokalemic primary aldosteronism (NPA) and in matched patients with normoreninemic essential hypertension (EH). The NPA patients showed an impaired ability to concentrate urine. By progresssively increasing C(osm) with saline loading, T(c/H2O) plateau both in NPA and in EH patients; in the former, however, the plateau occurred earlier and was lower than in the latter. In water diuresis, absolute values of C(H2O) were higher in NPA due to increased distal delivery secondary to impairment in proximal tubular reabsorption. Fractional C(H2O) (i.e. the ratio between C(H2O) and distal sodium delivery), however, was lower in NPA than in EH patients. Both in antidiuresis (after saline loading) and in water diuresis the NPA patients exhibited an enhanced fractional excretion of sodium. In one of NPA patients, clearance studies were repeated after adrenalectomy. In this patient, normalization of BP and reduction of body weight were associated with a rise in U(osm) and a reduction in C(osm) in antidiuresis; U(osm) and C(osm) were restored to pre-surgical values by expanding extracellular fluid volume (ECV) with saline loading. In summary our results suggest that ECV expansion is the mechanism by which urine concentration is impaired in patients with NPA.
|Number of pages||7|
|Publication status||Published - 1984|
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