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Nitric Oxide Decreases the Permselectivity of the Paracellular Pathway in Thick Ascending Limbs by Elevating cGMP Levels and Activating PKG
Author(s) -
Monzon Casandra,
Garvin Jeffrey
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.666.21
Subject(s) - paracellular transport , transcellular , chemistry , nitric oxide , dilution , endocrinology , biophysics , medicine , permeability (electromagnetism) , biochemistry , biology , membrane , physics , thermodynamics , organic chemistry
The thick ascending limb (TAL) reabsorbs 25‐30% of the filtered load of NaCl. About 70% is reabsorbed via the transcellular pathway and 30% is reabsorbed through the Na‐selective paracellular pathway. Nitric oxide (NO) inhibits net transepithelial and transcellular Na reabsorption, but its effects on the paracellular pathway are unknown. We hypothesized that NO decreases the permselectivity of the paracellular pathway for Na in TALs via cGMP and cGMP‐dependent protein kinase (PKG). To assess relative Na/Cl permeability ratios (P Na /P Cl ), we perfused TALs from Sprague Dawley rats and measured dilution potentials with and without NO donors (spermine NONOate: SPM, nitroglycerin: NTG) and dibutyryl cGMP (db‐cGMP). Dilution potentials were generated by reducing the bath NaCl concentration from 141 to 32 mM and P Na /P Cl was calculated using the Goldman‐Hodgkin‐Katz equation. During the control period, the dilution potential was ‐11.1 ± 2.1 mV and P Na /P Cl was 2.2 ± 0.4. After SPM (200 μM) treatment, they were ‐6.5 ± 1.6 mV (n = 9; p < 0.04) and 1.5 ± 0.2 (p < 0.03), respectively. NTG produced a similar effect on both dilution potential and P Na /P Cl . Time controls showed no significant changes. Db‐cGMP changed the dilution potential from ‐13.4 ± 2.9 to ‐7.5 ± 1.8 mV (n = 6; p < 0.01). In the presence of PKG inhibition with KT5823 (4 μM), SPM had no significant effect on dilution potentials (KT5823 alone: ‐8.6 ± 0.1 mV vs KT5823 + SPM: ‐7.1 ± 0.1 mV, N.S.; n = 6). KT5823 alone had no effect on dilution potentials. Phosphodiesterase 2 inhibition with BAY607550 (10 μM) did not block the effect of NO. We conclude that NO reduces the permselectivity of the paracellular pathway in TALs via cGMP and PKG. Funded by NIH HL28982.