Regulation of paracellular Na⁺ and Cl⁻ conductances by hydrostatic pressure

Abstract

The effect of hydrostatic pressure on the paracellular ion conductance (Gp) composed of the Na(+) conductance (G(Na)) and the Cl(-) conductance (G(Cl)) has been Investigated. Gp, G(Na) and G(Cl) were time-dependently increased after applying an osmotic gradient generated by NaCl with basolateral hypotonicity. Hydrostatic pressure (1-4cm H2O) applied from the basolateral side enhanced the osmotic gradient-induced increase in Gp, G(Na) and G(Cl) in a magnitude-dependent manner, while the hydrostatic pressure applied from the apical side diminished the osmotic gradient-induced increase in Gp, G(Na) and G(Cl). How the hydrostatic pressure influences Gp, G(Na) and G(Cl) under an isosmotic condition was also investigated. Gp, G(Na) and G(Cl) were stably constant under a condition with basolateral application of sucrose canceling the NaCl-generated osmotic gradient (an isotonic condition). Even under this stable condition, the basolaterally applied hydrostatic pressure drastically elevated Gp, G(Na) and G(Cl), while apically applied hydrostatic pressure had little effect on Gp, G(Na) or G(Cl). Taken together, these observations suggest that certain factors controlled by the basolateral osmolality and the basolaterally applied hydrostatic pressure mainly regulate the Gp, G(Na) and G(Cl).

Simulation of Cl− Secretion in Epithelial Tissues: New Methodology Estimating Activity of Electro-Neutral Cl− Transporter

“…We applied 100 μM NPPB (a non-selective Cl − channel blocker, Niisato and Marunaka, 1999 ) to the apical or basolateral solution for detection of the NPPB-sensitive conductance of the apical or basolateral membrane used as the Cl − conductance. We measured an NPPB-sensitive conductance (Niisato and Marunaka, 1999 ; Tokuda et al, 2007 , 2008 , 2009a , b , 2010 ). To detect the Cl − conductance of the apical membrane, we measured the NPPB-sensitive conductance by applying 100 μM NPPB to the apical solution 45 min after addition of 50 μM nystatin to the basolateral membrane that permeabilized the basolateral membrane.…”

Regulation of Epithelial Cell Functions by the Osmolality and Hydrostatic Pressure Gradients: A Possible Role of the Tight Junction as a Sensor

“…In the renal tubules, HP is applied from apical side by the flow of filtrate, and the HP gradient is known to affect various cell functions of Xenopus A6 cells [50,51]. The HP from basal side increases transepithelial conductance dependent on the degree of pressure.…”

Hypotonic stress upregulates β- and γ-ENaC expression through suppression of ERK by inducing MKP-1

“…Transepithelial potential (PD) was continuously measured by a high-impedance millivoltmeter that could function as a voltage clamp with automatic fluid resistance compensation (VCC-600, Physiologic Instruments, San Diego, CA) with a pair of calomel electrodes that were immersed in a saturated KCl solution and bridged to the modified Ussing chamber by a pair of polyethylene tubes filled with a solution of 2% (wt/vol) agarose in a 2 M KCl solution (18,19,22,38). I sc was measured by the amplifier (VCC-600) with a pair of silver-silver chloride electrodes that were immersed in a 2 M NaCl solution and bridged to the modified Ussing chamber by a pair of polyethylene tubes filled with a solution of 2% (wt/vol) agarose in a 2 M NaCl solution (1,(42)(43)(44).…”