In previous in vivo studies, pH in vasa recta blood in rat inner medulla was found to be acidic and pH in ascending (∼6.57) was lower than pH in descending (∼671) vasa recta blood under normal conditions. To determine if low pH was found in loop of Henle cells, we measured pHi in isolated nonperfused descending thin limb (DTL) and ascending thin limb (ATL) of Henle's loops from rat papilla using pH-sensitive fluorescent dye BCECF. Under control conditions (25 mM HEPES or 20 mM HEPES/5 mM bicarbonate buffer; pH 7.4), pHi in DTL (∼6.74) was lower than pHi in ATL (∼6.99) Addition of 20 mM NH4Cl to bath increased pHi to ∼7.37 and ∼7.49 in DTL and ATL, respectively. Removal of NH4Cl from bath reduced pHi to ∼6.66 and ∼6.77 in DTL and ATL, respectively. Rate of pH change (dpHi/df, pH U/s), intrinsic buffering capacity (βi, mM H+/pH U), base-lateral NH3 flux (JNH3, nmol/cm2/s), and basolateral NH3 permeability (PNH3, cm/s X 10-3) for DTL and ATL segments, respectively, were about: 0.25, 0.29; 28.0, 30.2; 4.1, 3.2; and 8.0, 6.5. Control recovery rate (dpHi/dt) from decreased pHi after NH4Cl removal was approximately 6.6 × 10-3 and 6.7 × 10-3 pH U/s in DTL and ATL segments, respectively. This dpHi/dt was decreased in DTL but not ATL by removal of Na+, Cl-, or Na+ and Cl- simultaneously. The acidic values for pHi and the differences in pHi between DTL and ATL are similar to pH values in what would be the neighboring ascending and descending vasa recta in vivo despite bath pH of 7.4 in vitro. These data raise questions about the regulation of pHi in Henle's loops in the rat inner medulla.
|Original language||English (US)|
|Publication status||Published - 1997|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology