title: Urinary plasmin activates collecting duct ENaC current in preeclampsia.
abstract: In nephrotic syndrome, plasminogen is aberrantly filtered from plasma to the urinary space and activated along the tubular system. In vitro, plasmin increases ENaC current by proteolytic cleavage of the γ-subunit. It was hypothesized that preeclampsia is associated with plasmin-dependent ability of tubular fluid to activate ENaC. Urine was sampled from 16 preeclamptic (PE) patients and 17 normotensive pregnant women (Ctrl). Urine was analyzed for plasmin(ogen), creatinine, albumin, aldosterone, Na(+), K(+), proteolytic activity, and for its effect on inward current in cortical collecting duct cells (M1 cells) by whole-cell patch clamp. In PE, urine plasmin(ogen): creatinine ratio was elevated 40-fold (geometric mean, 160 versus 4 µg/g; P<0.0001) and urine aldosterone: creatinine ratio was suppressed to 25% of Ctrl (geometric mean, 27 versus 109 µg/g; P<0.001). A significant negative correlation was found in PE between urinary plasmin(ogen) and aldosterone (P<0.05). In PE, proteolytic activity was detected at 90 to 75 kD by gelatin zymography in 14 of 16 patients and confirmed by serine protease assay. Immunoblotting showed active plasmin in PE urine. Whole-cell inward current increased in M1 cells on exposure to urine from PE (173±21%; n=6; P<0.001). The increase in current was abolished by amiloride (2 μmol/L; P<0.001), α(2)-antiplasmin (1 μmol/L; P<0.001), and heat denaturation (P<0.001). Preeclampsia is associated with urinary excretion of plasmin(ogen) and plasmin-dependent activation of ENaC by urine. Proteolytic activation of ENaC by plasmin may contribute to Na(+) retention and hypertension in preeclampsia.
authors.affiliation: Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, J. B. Winsløwsvej 21, 3. DK-5000, Odense C, Denmark.
authors.forename: Kristian B
authors.initials: KB
authors.lastname: Buhl
authors.forename: Ulla G
authors.initials: UG
authors.lastname: Friis
authors.forename: Per
authors.initials: P
authors.lastname: Svenningsen
authors.forename: Ambika
authors.initials: A
authors.lastname: Gulaveerasingam
authors.forename: Per
authors.initials: P
authors.lastname: Ovesen
authors.forename: Britta
authors.initials: B
authors.lastname: Frederiksen-Møller
authors.forename: Bente
authors.initials: B
authors.lastname: Jespersen
authors.forename: Claus
authors.initials: C
authors.lastname: Bistrup
authors.forename: Boye L
authors.initials: BL
authors.lastname: Jensen
mesh_terms: D000328:Adult; D000419:Albuminuria / Q000652:urine; D000450:Aldosterone / Q000652:urine; D015153:Blotting, Western; D003404:Creatinine / Q000652:urine; D003430:Cross-Sectional Studies; D053503:Epithelial Sodium Channels / Q000378:metabolism*; D005260:Female; D005341:Fibrinolysin / Q000652:urine*; D006801:Humans; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000652:urine; D011225:Pre-Eclampsia / Q000378:metabolism* / Q000503:physiopathology / Q000652:urine; D011247:Pregnancy; D059748:Proteolysis; D012964:Sodium / Q000652:urine
chemical_list: D053503:Epithelial Sodium Channels; D000450:Aldosterone; D012964:Sodium; D003404:Creatinine; D005341:Fibrinolysin; D011188:Potassium