title: Renal sodium transporter/channel expression and sodium excretion in P2Y2 receptor knockout mice fed a high-NaCl diet with/without aldosterone infusion.
abstract: The P2Y(2) receptor (P2Y2-R) antagonizes sodium reabsorption in the kidney. Apart from its effect in distal nephron, hypothetically, P2Y(2)-R may modulate activity/abundances of sodium transporters/channel subunits along the nephron via antagonism of aldosterone or vasopressin or interaction with mediators such as nitric oxide (NO), and prostaglandin E(2) (PGE(2)) or oxidative stress (OS). To determine the extent of the regulatory role of P2Y(2)-R in renal sodium reabsorption, in study 1, we fed P2Y(2)-R knockout (KO; n = 5) and wild-type (WT; n = 5) mice a high (3.15%)-sodium diet (HSD) for 14 days. Western blotting revealed significantly higher protein abundances for cortical and medullary bumetanide-sensitive Na-K-2Cl cotransporter (NKCC2), medullary α-1-subunit of Na-K-ATPase, and medullary α-subunit of the epithelial sodium channel (ENaC) in KO vs. WT mice. Molecular analysis of urine showed increased excretion of nitrates plus nitrites (NOx), PGE(2), and 8-isoprostane in the KO, relative to WT mice, supporting a putative role for these molecules in determining alterations of proteins involved in sodium transport along the nephron. To determine whether genotype differences in response to aldosterone might have played a role in these differences due to HSD, in study 2 aldosterone levels were clamped (by osmotic minipump infusion). Clamping aldosterone (with HSD) led to significantly impaired natriuresis with elevated Na/H exchanger isoform 3 in the cortex, and NKCC2 in the medulla, and modest but significantly lower levels of NKCC2, and α- and β-ENaC in the cortex of KO vs. WT mice. This was associated with significantly reduced urinary NOx in the KO, although PGE(2) and 8-isoprostane remained significantly elevated vs. WT mice. Taken together, our results suggest that P2Y(2)-R is an important regulator of sodium transporters along the nephron. Pre- or postreceptor differences in the response to aldosterone, perhaps mediated via prostaglandins or changes in NOS activity or OS, likely play a role.
authors.affiliation: Nephrology Research, Department of Veterans Administration Salt Lake City Health Care System, Departments of Medicine Georgetown University, Washington, District of Columbia, USA.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.forename: Raelene
authors.initials: R
authors.lastname: Listhrop
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Ecelbarger
authors.forename: Bellamkonda K
authors.initials: BK
authors.lastname: Kishore
mesh_terms: D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D015237:Dinoprost / Q000031:analogs & derivatives / Q000652:urine; D015232:Dinoprostone / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D023421:Models, Animal; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology; D058473:Receptors, Purinergic P2Y2 / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000378:metabolism*; D017673:Sodium Chloride, Dietary / Q000494:pharmacology*
chemical_list: D009566:Nitrates; D009573:Nitrites; D058473:Receptors, Purinergic P2Y2; D015222:Sodium Channels; D017673:Sodium Chloride, Dietary; C075750:8-epi-prostaglandin F2alpha; D009569:Nitric Oxide; D000450:Aldosterone; D012964:Sodium; D015237:Dinoprost; D019001:Nitric Oxide Synthase; D015232:Dinoprostone