Role of Apical H-K Exchange and Basolateral K Channel in the Regulation of Intracellular pH in Rat Distal Colon Crypt Cells

1998 ◽  
Vol 166 (3) ◽  
pp. 205-212 ◽  
Author(s):  
M. Ikuma *, † , H.J. Binder *, &#
Keyword(s):  
Intracellular Ph ◽  
Distal Colon ◽  
K Channel ◽  
Colon Crypt ◽  
Rat Distal Colon ◽  
Crypt Cells

Aldosterone-induced apical Na+ and K+ conductances are located predominantly in surface cells in rat distal colon

1994 ◽  
Vol 266 (1) ◽  
pp. G71-G82 ◽  
Author(s):  
R. B. Lomax ◽  
C. M. McNicholas ◽  
M. Lombes ◽  
G. I. Sandle
Keyword(s):  
Cell Population ◽  
Receptor Binding ◽  
Specific Binding ◽  
Distal Colon ◽  
Crypt Cell ◽  
K Channel ◽  
Surface Cell ◽  
Aldosterone Receptor ◽  
Rat Distal Colon ◽  
Crypt Cells

Aldosterone is a major regulator of Na(+)-absorptive and K(+)-secretory processes in the distal segment of mammalian colon. In this study, the distribution of aldosterone-sensitive cell types in isolated rat distal colon was determined using site-directed intracellular microelectrodes, specific Na(+)- and K(+)-channel blockers, and aldosterone-receptor binding techniques. Electrophysiological data indicated that aldosterone induced parallel apical membrane Na+ and K+ conductances, mainly in surface cells and to a significantly lesser degree in crypt cells. Scatchard analyses of aldosterone-receptor binding in cytosolic fractions revealed the maximum number of specific binding sites in whole mucosal homogenate and in the upper one-third and lower two-thirds of isolated crypt units to be 74.9 +/- 2.0, 59.8 +/- 2.4, and 59.3 +/- 3.2 fmol/mg protein, respectively, indicating the presence of aldosterone receptors in the crypt cell population. We conclude that in rat distal colon aldosterone-induced Na+ and K+ conductances (and by inference, electrogenic Na(+)-absorptive and K(+)-secretory processes) are located predominantly in the surface cell population and to a lesser extent in crypt cells, which also contain aldosterone receptors. This spectrum of aldosterone-induced Na+ and K+ conductances may reflect varying stages of differentiation along the surface cell-crypt cell axis.

Distribution and regulation of apical Cl/anion exchanges in surface and crypt cells of rat distal colon

1999 ◽  
Vol 276 (1) ◽  
pp. G132-G137 ◽  
Author(s):  
Vazhaikkurichi M. Rajendran ◽  
Henry J. Binder
Keyword(s):  
Spatial Distribution ◽  
Concentration Gradient ◽  
Apical Membrane ◽  
Membrane Vesicles ◽  
Distal Colon ◽  
Ph Homeostasis ◽  
Rat Distal Colon ◽  
Na Depletion ◽  
Crypt Cells ◽  
Apical Membrane Vesicles

Na depletion inhibits electroneutral Na-Cl absorption in intact tissues and Na/H exchange in apical membrane vesicles (AMV) of rat distal colon. Two anion (Cl/HCO3 and Cl/OH) exchanges have been identified in AMV from surface cells of rat distal colon. To determine whether Cl/HCO3 and/or Cl/OH exchange is responsible for vectorial Cl movement, this study examined the spatial distribution and the effect of Na depletion on anion-dependent 36Cl uptake by AMV in rat distal colon. These studies demonstrate that HCO3 concentration gradient-driven36Cl uptake (i.e., Cl/HCO3 exchange) is 1) primarily present in AMV from surface cells and 2) markedly reduced by Na depletion. In contrast, OH concentration gradient-driven36Cl uptake (i.e., Cl/OH exchange) present in both surface and crypt cells is not affected by Na depletion. In Na-depleted animals HCO3 also stimulates36Cl via Cl/OH exchange with low affinity. These results suggest that Cl/HCO3 exchange is responsible for vectorial Cl absorption, whereas Cl/OH exchange is involved in cell volume and/or cell pH homeostasis.

Comparison of aldosterone- and RU-28362-induced apical Na+ and K+ conductances in rat distal colon

1994 ◽  
Vol 267 (3) ◽  
pp. G485-G493 ◽  
Author(s):  
R. B. Lomax ◽  
G. I. Sandle
Keyword(s):  
Distal Colon ◽  
Distal Segment ◽  
K Channel ◽  
Rat Colon ◽  
Na Channel ◽  
Channel Blockers ◽  
Mineralocorticoid Antagonist ◽  
Channel Expression ◽  
K Secretion ◽  
Crypt Cells

In mammalian distal colon, aldosterone induces electrogenic Na+ absorption and electrogenic K+ secretion, whereas the sole transport effect of specific glucocorticoid agonists is thought to be stimulation of electroneutral NaCl absorption. In this study, intracellular microelectrodes and Na(+)- and K(+)-channel blockers were used to compare the effects of aldosterone and RU-28362 (a specific glucocorticoid agonist) on apical Na+ and K+ conductances in surface cells and upper crypt cells in the most distal colonic segment from adrenalectomized rats. In control animals, surface cells and crypt cells were devoid of apical Na+ and K+ conductances. In aldosterone-treated animals (70 micrograms.100 g body wt-1.day-1 for 7 days), Na+ conductances were induced in 88% of surface cells but only 40% of crypt cells, and the distribution of K+ conductances was similar (82% of surface cells and 50% of crypt cells). The same dose of RU-28362 also induced Na+ conductances in 82% of surface cells and 50% of crypt cells, which tended to be smaller than those induced by aldosterone. RU-28362, in contrast to aldosterone, had no effect on apical K+ conductance in surface cells or crypt cells. Concurrent treatment with the mineralocorticoid antagonist RU-28318 (3.5 mg.100 g body wt-1.day-1 for 7 days) inhibited Na(+)-channel expression in aldosterone-treated animals but had no effect in RU-28362-treated animals. We conclude that in the most distal segment of rat colon, aldosterone acts via mineralocorticoid receptors to induce apical Na+ and K+ conductances, which are only fully expressed in the surface cell population.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of intracellular pH in crypt cells from rabbit distal colon

1994 ◽  
Vol 267 (3) ◽  
pp. G409-G415 ◽  
Author(s):  
S. L. Abrahamse ◽  
A. Vis ◽  
R. J. Bindels ◽  
C. H. van Os
Keyword(s):  
Intracellular Ph ◽  
Distal Colon ◽  
Buffering Capacity ◽  
Colonic Crypt ◽  
Bafilomycin A1 ◽  
Acid Load ◽  
Intracellular Buffering Capacity ◽  
Crypt Cells ◽  
Exchange Activity ◽  
In Cells

H+ secretory mechanisms and intrinsic intracellular buffering capacity were studied in crypt cells from rabbit distal colon. To this end crypts of Lieberkuhn were isolated by microdissection, and intracellular pH (pHi) was measured using digital imaging fluorescence microscopy and the pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)- 5(6)-carboxyfluorescein. In the absence of HCO(3-)-CO2 and presence of Na+, resting pHi was 7.51 +/- 0.04 (n = 237/23, cells/crypts). However, 6 min after superfusion with a solution containing zero Na+, 1 x 10(5) M Sch-28080 and 5 x 10(-8) M bafilomycin A1, pHi in cells at the bottom of the crypts was significantly reduced, whereas pHi in cells at the top of the crypts remained unchanged. The intrinsic buffering capacity of cells from the middle to the top portion of crypts was significantly higher in the pHi range 7.2-7.6 than of cells at the bottom of the crypt. H+ secretion after an NH(4+)-NH3 pulse amounted to 245 +/- 53 microM/s (n = 73/7) at pHi 7.1 and was largely Na+ dependent and ethylisopropylamiloride sensitive. The Na(+)-independent recovery of pHi after an acid load was insensitive to Sch-28080 and bafilomycin A1. In conclusion, pHi in colonic crypt cells is regulated through Na+/H+ exchange activity in the absence of HCO3-. In addition, intracellular buffering capacity varied with the position along the crypt axis, whereas Na+/H+ exchange activity and pHi did not.

Characterization of apical membrane Cl-dependent Na/H exchange in crypt cells of rat distal colon

2001 ◽  
Vol 280 (3) ◽  
pp. G400-G405 ◽  
Author(s):  
Vazhaikkurichi M. Rajendran ◽  
John Geibel ◽  
Henry J. Binder
Keyword(s):  
Channel Blocker ◽  
Apical Membrane ◽  
Distal Colon ◽  
Proton Gradient ◽  
Disulfonic Acid ◽  
High Dose ◽  
Cl Channel ◽  
Rat Distal Colon ◽  
Na Uptake ◽  
Crypt Cells

A novel Cl-dependent Na/H exchange (Cl-NHE) has been identified in apical membranes of crypt cells of rat distal colon. The presence of Cl is required for both outward proton gradient-driven Na uptake in apical membrane vesicles (AMV) and Na-dependent intracellular pH recovery from an acid load in the crypt gland. The present study establishes that Cl-dependent outward proton gradient-driven 22Na uptake 1) is saturated with increasing extravesicular Na concentration with a Michaelis constant ( K m) for Na of ∼24.2 mM; 2) is saturated with increasing outward H concentration gradient with a hyperbolic curve and a K m for H of ∼1.5 μM; 3) is inhibited by the Na/H exchange (NHE) inhibitors amiloride, ethylisopropylamiloride, and HOE-694 with an inhibitory constant ( K i) of ∼480.2, 1.1, and 9.5 μM, respectively; 4) is inhibited by 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid, an anion exchange inhibitor at low concentration and a Cl channel blocker at high dose, and by 5-nitro-2(3-phenylpropylamino)benzoic acid, a Cl channel blocker, with a K i of ∼280.6 and 18.3 μM, respectively; and 5) substantially stimulated Cl-NHE activity by dietary Na depletion, which increases plasma aldosterone and inhibits NHE in surface cell AMV. These properties of Cl-NHE are distinct from those of NHE1, NHE2, and NHE3 isoforms that are present in colonic epithelial cells; thus these results suggest that the colonic crypt cell Cl-NHE is a novel NHE isoform.

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