Urinary prostasin: a candidate marker of epithelial sodium channel activation in humans.
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.
Olivieri
Oliviero
O
Department of Clinical and Experimental Medicine, University of Verona, Italy. oliviero.olivieri@univr.it
Castagna
Annalisa
A
Guarini
Patrizia
P
Chiecchi
Laura
L
Sabaini
Gherardo
G
Pizzolo
Francesca
F
Corrocher
Roberto
R
Righetti
Pier Giorgio
PG
D000328:Adult; D000368:Aged; D000450:Aldosterone / Q000097:blood; D015415:Biomarkers / Q000652:urine; D015153:Blotting, Western; D016022:Case-Control Studies; D004232:Diuretics / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D053503:Epithelial Sodium Channels; D005260:Female; D005438:Fludrocortisone / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D006929:Hyperaldosteronism / Q000652:urine; D006973:Hypertension / Q000097:blood / Q000378:metabolism* / Q000652:urine; D008297:Male; D008875:Middle Aged; D011188:Potassium / Q000652:urine; D012083:Renin / Q000097:blood; D012697:Serine Endopeptidases / Q000652:urine*; D012964:Sodium / Q000652:urine; D015222:Sodium Channels / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D012982:Sodium, Dietary / Q000008:administration & dosage / Q000494:pharmacology; D013148:Spironolactone / Q000494:pharmacology; D000099271:Prostasin
D000450:Aldosterone; D015415:Biomarkers; D004232:Diuretics; D053503:Epithelial Sodium Channels; D005438:Fludrocortisone; D011188:Potassium; D012083:Renin; D012697:Serine Endopeptidases; D012964:Sodium; D015222:Sodium Channels; D012965:Sodium Chloride; D012982:Sodium, Dietary; D013148:Spironolactone; D000099271:Prostasin; C034635:fludrocortisone acetate