Nitric oxide reduces paracellular resistance in rat thick ascending limbs by increasing Na⁺ and Cl⁻ permeabilities

Abstract

About 50% of the Na reabsorbed in thick ascending limbs traverses the paracellular pathway. Nitric oxide (NO) reduces the permselectivity of this pathway via cGMP, but its effects on absolute Na ([Formula: see text]) and Cl ([Formula: see text]) permeabilities are unknown. To address this, we measured the effect of l-arginine (0.5 mmol/l; NO synthase substrate) and cGMP (0.5 mmol/l) on [Formula: see text] and [Formula: see text] calculated from the transepithelial resistance () and [Formula: see text]/[Formula: see text] in medullary thick ascending limbs. was 7,722 ± 1,554 ohm·cm in the control period and 6,318 ± 1,757 ohm·cm after l-arginine treatment ( < 0.05). [Formula: see text]/[Formula: see text] was 2.0 ± 0.2 in the control period and 1.7 ± 0.1 after l-arginine ( < 0.04). Calculated [Formula: see text] and [Formula: see text] were 3.52 ± 0.2 and 1.81 ± 0.10 × 10 cm/s, respectively, in the control period. After l-arginine they were 6.65 ± 0.69 ( < 0.0001 vs. control) and 3.97 ± 0.44 ( < 0.0001) × 10 cm/s, respectively. NOS inhibition with -nitro-l-arginine methyl ester (5 mmol/l) prevented l-arginine's effect on Next we tested the effect of cGMP. in the control period was 7,592 ± 1,470 and 4,796 ± 847 ohm·cm after dibutyryl-cGMP (0.5 mmol/l; db-cGMP) treatment ( < 0.04). [Formula: see text]/[Formula: see text] was 1.8 ± 0.1 in the control period and 1.6 ± 0.1 after db-cGMP ( < 0.03). [Formula: see text] and [Formula: see text] were 4.58 ± 0.80 and 2.66 ± 0.57 × 10 cm/s, respectively, for the control period and 9.48 ± 1.63 ( < 0.007) and 6.01 ± 1.05 ( < 0.005) × 10 cm/s, respectively, after db-cGMP. We modeled NO's effect on luminal Na concentration along the thick ascending limb. We found that NO's effect on the paracellular pathway reduces net Na reabsorption and that the magnitude of this effect is similar to that due to NO's inhibition of transcellular transport.

Thick Ascending Limb Sodium Transport in the Pathogenesis of Hypertension

“…The three NOS isoforms, NOS1, NOS2, and NOS3, were formerly known as neuronal NOS, inducible NOS, and endothelial NOS, respectively, based on the tissue or conditions in which they were first characterized. All three NOS isoforms are found in thick ascending limbs (208,562,714), where NO regulates net NaCl reabsorption through inhibition of both transcellular and paracellular pathways (455,456,502,506,543). Given the central role that NO plays in regulating thick ascending limb salt reabsorption, in addition to the fact that its production or actions in Dashed lines indicate that the complete signaling cascade is unknown.…”

“…Additionally, patch-clamp data show that NO stimulates apical 70-pS ROMK channels in this segment (402,731) Mathematical modeling allowed us to predict how the actions of NO affected the luminal Na ϩ concentration along the thick ascending limb (456). At the end of the tubule, NO treatment resulted in a higher luminal concentration of Na ϩ compared with the absence of NO treatment.…”

A perfusion chamber for monitoring transepithelial NaCl transport in an in vitro model of the renal tubule

“…and 844 ± 397 Ω cm 2 (−Grad.). There are no reported values for this cell line, but TEER for freshly isolated rat medullary TAL tubules is one order of magnitude lower (7,722 Ω cm, corresponding to 48 Ω cm 2 for lumen diameter of 20 μm) (Monzon, Occhipinti, Pignataro, & Garvin, ). Interestingly, TEER of raTAL cells increased during the negative gradient and decreased during the positive gradient although not significantly.…”

Claudin-19 mediates the effects of NO on the paracellular pathway in thick ascending limbs

“…NO inhibits transcellular Na ϩ reabsorption by decreasing the activity of both the Na ϩ -K ϩ -2Cl Ϫ cotransporter and Na ϩ /H ϩ exchanger via signaling cascades involving cGMP/phosphodiesterase 2 and cGMP/PKG, respectively (25,26). We have previously reported that NO also affected the paracellular pathway in such a manner that it was predicted to reduce paracellular Na ϩ reabsorption in vivo (24). This effect was mediated by cGMPand PKG (23).…”