Mechanisms of intracellular pH regulation in the hamster inner medullary collecting duct perfused in vitro.
To examine the mechanisms of H+ transport in the mid-inner medullary collecting duct of hamsters, we measured the intracellular pH (pHi) in the in vitro perfused tubules by microscopic fluorometry using 2',7'-bis(carboxyethyl)-carboxyfluorescein (BCECF) as a fluorescent probe. In the basal condition, pHi was 6.74 +/- 0.04 (n = 45) in HCO3(-)-free modified Ringer solution. Either elimination of Na+ from the bath or addition of amiloride (1 mM) to the bath produced a reversible fall in pHi. After acid loading with 25 mM NH4Cl, pHi spontaneously recovered with an initial recovery rate of 0.096 +/- 0.012 (n = 23) pH unit/min. In the absence of ambient Na+, after removal of NH+4, the pHi remained low (5.95 +/- 0.10, n = 8) and showed no signs of recovery. Subsequent restoration of Na+ only in the lumen had no effect on pHi. However, when Na+ in the bath was returned to the control level, pHi recovered completely Amiloride (1 mM) in the bath completely inhibited the Na(-)-dependent pHi recovery. Furthermore, elimination of Na+ from the bath, but not from the lumen, decreased pHi from 6.97 +/- 0.07 to 6.44 +/- 0.05 (n = 12) in the HCO3-/Ringer solution or 6.70 +/- 0.03 to 6.02 +/- 0.5 pH unit/min in the presence of CO2/HCO3-, whereas it did not recover in the absence of CO2/HCO3-.(ABSTRACT TRUNCATED AT 250 WORDS)
Matsushima
Y
Y
Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, Osaka, Japan.
Yoshitomi
K
K
Koseki
C
C
Kawamura
M
M
Akabane
S
S
Imanishi
M
M
Imai
M
M
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002352:Carrier Proteins / Q000502:physiology; D006224:Cricetinae; D005452:Fluoresceins; D005470:Fluorometry; D006863:Hydrogen-Ion Concentration; D007685:Kidney Tubules, Collecting / Q000378:metabolism / Q000502:physiology*; D008297:Male; D008647:Mesocricetus; D010477:Perfusion; D017923:Sodium-Hydrogen Exchangers
D002352:Carrier Proteins; D005452:Fluoresceins; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein