Volume‐regulatory Cl‐ channel currents in cultured human epithelial cells.

Abstract

SUMMARY1. During osmotic swelling, cultured human small intestinal epithelial cells (Intestine 407) exhibited activation of large Cl-currents under the patch-clamp whole-cell configuration. The volume-sensitive Cl-conductance was independent of intracellular Ca2+ and cyclic AMP.2. The anion permeability sequence of the current was SCN-> I-> Br-> Cl-> F-> gluconate-, corresponding to Eisenman's sequence I. 3. Cl-currents were instantaneously activated by command pulses in a range of -120 to + 45 mV. At potentials more positive than + 50 mV the current showed a time-dependent inactivation. This inactivation was accelerated by increased depolarization. The instantaneous current-voltage relationship rectified in the outward direction.4. A stilbene-derivative Cl-channel blocker, 4-acetamido-4'-isothiocyanostilbene (SITS), inhibited the Cl-current at micromolar concentrations. SITS facilitated inactivation at positive potentials. Outward currents were more prominently suppressed by SITS than inward currents. The concentrations required for 50% inhibition (IC50) of outward and inward currents were 1-5 and 6 EM, respectively. The outward and inward currents were equally inhibited by a carboxylate analogue Clchannel blocker, 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB)

Extracellular acidification elicits a chloride current that shares characteristics with ICl(swell)

“…The level of inhibition of I Cl(pHac) was similar to that described on application of 500 M DPC in Sertoli cells (3). In contrast, the level of inhibition of I Cl(swell) apparently differed from the value of an IC 50 of 350 M reported for a small intestinal human epithelial cell line (22) and an IC 50 of 200 M for cultured chick heart cells (48). These differences are presumably attributable to the different cell types used in the mentioned studies.…”

“…DPC was recently shown to inhibit a Cl Ϫ current activated by extracellular acidification in Sertoli cells (3) as well as I Cl(swell) (22). In the presence of 500 M DPC, the mean maximum current, measured at ϩ120 mV, for I Cl(swell) was 13.5 Ϯ 0.17 pA/pF (n ϭ 3) vs. a control of 114 Ϯ 27.84 pA/pF (n ϭ 13) and for I Cl(pHac) was 6.6 Ϯ 1.5 pA/pF (n ϭ 3) vs. a Fig.…”

“…The relative anion selectivity for the swelling-activated Cl Ϫ channel is SCN Ϫ Ͼ I Ϫ Ͼ Br Ϫ Ͼ Cl Ϫ Ͼ F Ϫ Ͼ gluconate; this sequence is referred to as "Eisenman sequence I" and indicates a weak interaction between the channel pore and the permeation anion. A number of different substances, including the stilbene derivative 4,4Ј-diisothiocyanostilbene-2,2Ј-disulfonic acid (DIDS) (9,35), the anti-inflammatory drug niflumic acid (20), the antiestrogen drug tamoxifen (43), diphenylamine-2-carboxylic acid (DPC) (22), and 1,9-dideoxyforskolin (DDFSK) (9), inhibit I Cl(swell) . Furthermore I Cl(swell) is insensitive to changes in calcium concentrations (33).…”

TMEM16F is a component of a Ca2+-activated Cl− channel but not a volume-sensitive outwardly rectifying Cl− channel

“…Human cervix HeLa cells were cultured in minimum essential medium (Sigma, St. Louis, MO) containing 10% FBS as well as penicillin and streptomycin at the same concentrations as above. Human epithelial Intestine 407 cells were cultured as previously reported (13).…”

Differential dependence of regulatory volume decrease behavior in rabbit corneal epithelial cells on MAPK superfamily activation

“…As in a number of different vertebrate cells, we found in RCEC that K + and Cl − channel activation contributes to the RVD response (Christensen and Hoffmann, 1992;Furuya et al, 1989;Hazama and Okada, 1988;Kubo and Okada, 1992). Unlike the relationship between activation of MAPK signaling and RVD in any other tissue described in the literature, RVD is dependent on activation of the ERK and SAPK/JNK branches of the MAPK cascade.…”