Regulation of intracellular pH in rat renal inner medullary thin limbs of Henle’s loop

Abstract

Regulation of intracellular pH (pHi) was studied in isolated rat renal inner medullary thin limbs of Henle's loop in bicarbonate/phosphate-buffered medium with high pCO2, high osmolality ( congruent with670 mosmol/kg H2O; 270 mM urea; 180 mM NaCl), organic osmolytes, and a pH of 6.8 to approximate the physiological in vivo environment. The pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF) was used to measure pHi. Resting pHi was always acid and significantly more acid in descending thin limb (DTL) cells than in ascending thin limb (ATL) cells from pure or mixed-type thin limbs. Resting pHi was slightly but significantly higher in both DTLs and ATLs in high osmolality ( approximately 670 mosmol/kg H2O) than in low osmolality ( approximately 290 mosmol/kg H2O) medium but not when sucrose replaced urea. In both DTLs and ATLs the rate of recovery of pHi following additional acidification with an NH4Cl pulse was reduced by Na+ removal from the medium and by the addition of 60 microM HOE642 (an inhibitor of the Na+/H+ exchanger, NHE1), 55 microM S1611 (inhibitor of Na+/H+ exchanger, NHE3), 1 microM bafilomycin A1 (an inhibitor of vacuolar H+ -ATPase), or 20 microM Schering 28080 (an inhibitor of H+ -K+ -ATPase) to the medium. Resting pHi was also reduced by 60 microM HOE642, 55 microM S1611, and 20 microM Schering 28080. In both DTLs and ATLs, RT-PCR revealed message for NHE1, NHE3, and vacuolar H+ -ATPase; immunocytochemistry demonstrated the expression of the protein for NHE1 (basolateral membrane), NHE3 (luminal membrane), and H+ -K+ -ATPase (luminal membrane). These data suggest that pHi in rat inner medullary thin limbs is regulated by urea and by basolateral and luminal H+ extrusion via NHE1, NHE3, vacuolar H+ -ATPase, and H+ -K+ -ATPase.

Systematic expression profiling of the gastric H+/K+ATPase in human tissue

“…As expected, expression was stronger in renal medulla than in cortex (Figures 4 and 6). This is in line with the current literature [28,29].…”

Nongenomic Effects of Aldosterone on Renal Protein Expressions of pEGFR and pERK1/2 in Rat Kidney

“…A previous study on the renal inner medulla tLH has been demonstrated to express NHE1, NHE3, and H,K-ATPase [24]. The present study is the first to delineate that aldosterone could rapidly elevate the pEGFR-pERK1/2 cascade in this segment of the rat kidney.…”

Renal Vacuolar H+-ATPase

“…Both apical and basolateral membranes were labeled. A bafilomycin-sensitive vacuolar H ϩ -ATPase has also been detected by functional measurements in this initial segment (407). No other segments of long or short thin limbs have been reported to contain the vacuolar H ϩ -ATPase.…”