Effects of in vivo and in vitro alkali treatment on intracellular pH regulation of OMCDis cells.
To examine functional changes of the transporters in the inner stripe of the outer medullary collecting ducts (OMCDis) by the peritubular acid-base status, in vitro microperfusion using the acetoxymethyl ester of 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein was performed. Cell alkalinization systems were assessed by the recovery rate (dpHi/dt) of intracellular pH (pHi) after intracellular acid loading by NH(4+)-NH3 prepulse with bath amiloride. In alkali-loaded rabbits (0.15 M NaHCO3 drinking for 14 days), dpHi/dt showed a significant decrease (1.80 +/- 0.29 pH units/s x 10(3)) compared with either control (3.30 +/- 0.59) or acid-loaded rabbits (0.15 M NH4Cl drinking for 14 days, 3.05 +/- 0.46). The difference of dpHi/dt between control and alkali-loaded rabbits was eliminated by lumen N-ethylmaleimide (NEM), suggesting that H+ pump activity was decreased. The effect of in vitro alkali treatment (50 mM HCO3-, pH 7.7) for 3-4 h was also examined. This incubation significantly decreased the dpHi/dt (1.83 +/- 0.35) compared with the time control experiments (3.18 +/- 0.28), whereas no significant difference was seen in the presence of lumen NEM. Anion exchanger activity, as determined from the pHi changes after Cl- addition to the bath, showed no significant change with in vivo or in vitro alkali treatment. The results indicate that cell function of the OMCDis is regulated in response to the peritubular acid-base environment via changes in the H(+)-adenosinetriphosphatase.
Hayashi
M
M
Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan.
Iyori
M
M
Yamaji
Y
Y
Saruta
T
T
D000584:Amiloride / Q000494:pharmacology; D000641:Ammonia / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D005033:Ethylmaleimide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000187:drug effects / Q000502:physiology; D007679:Kidney Medulla / Q000187:drug effects / Q000502:physiology*; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D011817:Rabbits
D007093:Imidazoles; C035235:Sch 28080; D000643:Ammonium Chloride; D002245:Carbon Dioxide; D000641:Ammonia; D000584:Amiloride; D005033:Ethylmaleimide; D010100:Oxygen