Objective: Prostasin is a GPI-anchored serine protease involved in Epithelium Na Channel (ENaC) activation and released in urine. A direct association between urinary prostasin concentration and the activation of the aldosterone-driven pathway has been suggested.Purpose are;verify i) if urinary prostasin concentrations are higher in patients with primary aldosteronism (PA) than in patients with essential hypertension (EH), ii) to investigate the relation between prostasin and natriuresis in hypertensive patients with or without PA. Design and method: We enrolled 106 patients (65 M, 41F) who were investigated for possible secondary causes of hypertension and underwent aldosterone to renin ratio (ARR) screening at the Hypertension Unit of the University Hospital of Verona. Prostasin concentration was measured by an ELISA assay, based on the antibody sandwich principle utilizing a “capture” antibody and a “detection” antibody, both antibodies commercially available. Results: Prostasin was higher in urine of PA than EH patients. Prostasin was positively correlated with aldosterone to renin ratio (ARR), inversely with plasma potassium and urinary sodium. The u- prostasin/Na ratio in the highest quartile is associated with a 15 fold probability of PA diagnosis in hypertensive patients Conclusions: Unlike normotensive subjects in whom prostasin and natriuresis are directly correlated, in PA patients prostasin increases as u-Na decreases, suggesting a disproportional ENaC activation in spite of the hypertensive state and expanded volume. PA patients are thus characterized by a specific urinary pattern of high prostasin and low sodium suggesting that urinary prostasin grossly reflects the extent of aldosterone-dependent ENaC over-activation.

Objective: Prostasin is a GPI-anchored serine protease involved in Epithelium Na Channel (ENaC) activation and released in urine. A direct association between urinary prostasin concentration and the activation of the aldosterone-driven pathway has been suggested.Purpose are;verify i) if urinary prostasin concentrations are higher in patients with primary aldosteronism (PA) than in patients with essential hypertension (EH), ii) to investigate the relation between prostasin and natriuresis in hypertensive patients with or without PA. Design and method: We enrolled 106 patients (65 M, 41F) who were investigated for possible secondary causes of hypertension and underwent aldosterone to renin ratio (ARR) screening at the Hypertension Unit of the University Hospital of Verona. Prostasin concentration was measured by an ELISA assay, based on the antibody sandwich principle utilizing a “capture” antibody and a “detection” antibody, both antibodies commercially available. Results: Prostasin was higher in urine of PA than EH patients. Prostasin was positively correlated with aldosterone to renin ratio (ARR), inversely with plasma potassium and urinary sodium. The u- prostasin/Na ratio in the highest quartile is associated with a 15 fold probability of PA diagnosis in hypertensive patients Conclusions: Unlike normotensive subjects in whom prostasin and natriuresis are directly correlated, in PA patients prostasin increases as u-Na decreases, suggesting a disproportional ENaC activation in spite of the hypertensive state and expanded volume. PA patients are thus characterized by a specific urinary pattern of high prostasin and low sodium suggesting that urinary prostasin grossly reflects the extent of aldosterone-dependent ENaC over-activation.

Pizzolo, F.; Raffaelli, R.; Chiecchi, L.; Memmo, A.; Consoli, L.; Stanzial, A. M.; Guarini, P.; Guidi, G. C.; Franchi, M.; Olivieri, O. Author Information

Chiecchi, L.1; Pizzolo, F.1; Kitamura, K.2; Raffaelli, R.1; Consoli, L.1; Gunasekaran, M.1; Castagna, A.1; Salvagno, G.1; Guarini, P.1; Olivieri, O.1 Author Information

Objectives Due to the widespread use of the aldosterone to renin ratio (ARR), primary aldosteronism is currently recognized as a frequent cause of secondary hypertension. After a positive screening, primary aldosteronism diagnosis needs confirmation by an inhibitory test such as intravenous saline load (ivSLT). The aim of the present study was to investigate the role of female hormones in primary aldosteronism diagnosis, by evaluating possible differences by sex on ARR screening, on the rate of ivSLT response and analyzing the influence of free and oral contraceptive-induced menstrual cycle on ARR. Methods We examined ARR in 103 healthy normotensive volunteers, 81 hypertensive patients who underwent ivSLT, 33 healthy women during free menstrual cycle and after oral contraceptive therapy. Results A significantly higher proportion of normotensive women than men had an elevated ARR (13.6 versus 2.3%, P < 0.05). In 44 out of 81 hypertensive patients, diagnosis of primary aldosteronism was confirmed by ivSLT. Patients with positive and negative ivSLT differed only for sex distribution: 85.2% of men had the primary aldosteronism diagnosis confirmed, compared with 38.9% of women. In healthy women, renin and aldosterone concentrations increased from the follicular to luteal phase of menstrual period, with unchanged ARR. By contrast, renin nearly halved, aldosterone slightly decreased and ARR doubled after oral contraceptive therapy. Conclusion ARR screening fails to predict positive ivSLT in most (60.2%) hypertensive women as compared with 14.8% of hypertensive men. ARR is more often increased in normotensive women than men. Oral contraceptive may affect ARR contributing to the diagnostic inaccuracy in women.

Prostasin is a serine peptidase hypothesized to regulate epithelial sodium channel (ENaC) activity in animals or on in vitro cultured cells. We investigated whether urinary prostasin may be a candidate marker of ENaC activation in humans. We studied 10 healthy volunteers and 8 hypertensive patients with raised aldosterone-to-renin ratio before and after spironolactone or saline/Florinef suppression test, respectively. Four healthy subjects were also studied before and after saline. Urinary prostasin was evaluated by SDS-PAGE, 2D maps, and Western blotting. Every sample of normotensive individuals was compared with the corresponding sample of urine collected after spironolactone or saline; every sample of hypertensive patients was compared with the corresponding sample of urine collected after saline or Florinef. Prostasin was detectable in all subjects regardless of gender, dietary sodium intake, and spironolactone treatment. Spironolactone (100 mg) increased urinary Na+/K+ ratio and decreased urinary prostasin in normotensives in whom the renin/aldosterone axis was activated by a low Na+ intake, but it was ineffective in individuals with high Na+ intake. Saline infusion also reduced prostasin in normotensive subjects. In contrast, prostasin paradoxically increased in urine of patients affected by primary aldosteronism after volume expansion. By 2D immunoblotting, several protein isoforms were observed, some of them being overexpressed after inhibition tests in patients with primary aldosteronism. In addition to a "basal" aliquot of prostasin, constitutively released in human urine regardless of sodium balance and aldosterone activation, there exists a second "aldosterone-responsive" aliquot modulated by Na+ intake and potentially suitable as candidate marker of ENaC activation.