title: Chloride-dependent intracellular pH regulation via extracellular calcium-sensing receptor in the medullary thick ascending limb of the mouse kidney.
abstract: The extracellular calcium-sensing receptor (CaSR) located in either luminal or basolateral cell membranes of various types of renal tubules including proximal tubules, Henle's loop and collecting ducts has been thought to play a fundamental role in electrolyte metabolism. To further identify the physiological roles of the CaSR, we examined the effects of Ca(2+) and calcimimetics neomycin (Neo), gentamicin and gadolinium chloride (Gd(3+)) on the intracellular pH (pHi) of in vitro microperfused mouse medullary thick ascending limb (mTAL) cells of Henle's loop, by loading the cells with fluorescent pH indicator 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein and measuring the ratio of fluorescence emission at 530 nm after exciting the dye at 490 and 440 nm. In a steady-state condition in Hepes-buffered solution, the pHi in the mTALs was 7.29 +/- 0.04 (n = 9). A concentration of 200 micromol/l Neo in the basolateral side decreased the pHi after 1 min by -0.13 +/- 0.02 (n = 34, p < 0.0001). The other calcimimetics showed similar effects on pHi, whereas none of these calcimimetics in the lumen affected pHi. Na(+) removal or the inhibition of Na(+) and proton transport with amiloride, bumetanide, or bafilomycin did not eliminate the effect of Neo on pHi. On the other hand, Cl(-) removal clearly eliminated the Neo-induced pHi decrease (-0.06 +/- 0.01 vs -0.00 +/- 0.05 in Cl(-) removal, n = 4, p < 0.003). Thus, we have demonstrated for the first time that the CaSR is involved in the regulation of the pHi in the mTAL and requires Cl(-) to exert its effect.
authors.affiliation: Department of Pediatrics, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Ulviyya Fizuli
authors.initials: UF
authors.lastname: Aslanova
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Morimoto
authors.forename: Elnur Ilham
authors.initials: EI
authors.lastname: Farajov
authors.forename: Naonori
authors.initials: N
authors.lastname: Kumagai
authors.forename: Minako
authors.initials: M
authors.lastname: Nishino
authors.forename: Noriko
authors.initials: N
authors.lastname: Sugawara
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ohsaga
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Maruyama
authors.forename: Shigeru
authors.initials: S
authors.lastname: Tsuchiya
authors.forename: Shori
authors.initials: S
authors.lastname: Takahashi
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Kondo
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D052139:Intracellular Calcium-Sensing Proteins / Q000502:physiology*; D007424:Intracellular Fluid / Q000502:physiology*; D008138:Loop of Henle / Q000166:cytology / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL
chemical_list: D002712:Chlorides; D052139:Intracellular Calcium-Sensing Proteins; D002118:Calcium