title: NKCC2 is activated in Milan hypertensive rats contributing to the maintenance of salt-sensitive hypertension.
abstract: The Milan hypertensive strain of rats (MHS) develops hypertension as a consequence of the increased tubular Na(+) reabsorption sustained by enhanced expression and activity of the renal tubular Na-K-ATPase. To verify whether the Na-K-2Cl cotransporter (NKCC2) is involved in the maintenance of hypertension in MHS rats, we have analysed the phosphorylation state and the activation of NKCC2 in Milan rats. Western blotting and immunofluorescence experiments were performed using specific antibodies against the regulatory phospho-threonines in the NKCC2 N terminus (R5 antibody). The phosphorylation levels of NKCC2 were significantly increased in the kidney of MHS rats. Moreover, the administration of furosemide in vivo decreased the blood pressure and increased the urine output and natriuresis in MHS rats demonstrating the actual involvement of NKCC2 activity in the pathogenesis of hypertension in this strain of rats. The up-regulation of NKCC2 activity is most probably mediated by a STE20/SPS1-related proline/alanine-rich kinase (SPAK) phosphorylation at serine-325 since it was significantly increased in MHS rats. Interestingly, aldosterone treatment caused an increase in NKCC2 phosphorylation in NKCC2-expressing MDCK cells. In conclusion, we demonstrated an increase in the activity of NKCC2 along the TAL that significantly contributes to the increase in systemic blood pressure in MHS rats. The elevated plasma levels of aldosterone, found in MHS rats, may influence Na(+) balance through a SPAK-dependent regulation of NKCC2 accounting for the maintenance of the hypertensive state in MHS rats.
authors.affiliation: General and Environmental Physiology, University of Bari, Bari, Italy. monica.carmosino@uniba.it
authors.forename: Monica
authors.initials: M
authors.lastname: Carmosino
authors.forename: Federica
authors.initials: F
authors.lastname: Rizzo
authors.forename: Patrizia
authors.initials: P
authors.lastname: Ferrari
authors.forename: Lucia
authors.initials: L
authors.lastname: Torielli
authors.forename: Mara
authors.initials: M
authors.lastname: Ferrandi
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Bianchi
authors.forename: Maria
authors.initials: M
authors.lastname: Svelto
authors.forename: Giovanna
authors.initials: G
authors.lastname: Valenti
mesh_terms: D000450:Aldosterone / Q000097:blood / Q000652:urine; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D004232:Diuretics / Q000494:pharmacology; D005665:Furosemide / Q000494:pharmacology; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D008297:Male; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012965:Sodium Chloride / Q000378:metabolism*; D012982:Sodium, Dietary / Q000378:metabolism*; D028021:Sodium-Potassium-Chloride Symporters / Q000235:genetics / Q000378:metabolism*; D064466:Solute Carrier Family 12, Member 1; D014556:Urine / Q000737:chemistry
chemical_list: D004232:Diuretics; C578714:SLC12A1 protein, human; C578716:Slc12a1 protein, rat; D012982:Sodium, Dietary; D028021:Sodium-Potassium-Chloride Symporters; D064466:Solute Carrier Family 12, Member 1; D012965:Sodium Chloride; D000450:Aldosterone; D005665:Furosemide; C116037:PAS domain kinases; D017346:Protein Serine-Threonine Kinases