Low‐conductance chloride channel activated by cAMP in the epithelial cell line T₈₄

Abstract

We have studied the modulation and pharmacological properties of two anion channels in T, ceils by recording single channel and transepithelial currents. One channel had an outwardly rectifying current-voltage Z/V curve, was rarely active in cell-attached patches, and was unaffected by CAMP. The other channel had lower conductance (8.7 pS at 37°C) and a more ohmic Z/V relationship. Exposure to CAMP increased the probability of observing low-conductance channel activity in cell-attached patches > 6-fold. Extracellular DIDS (4,4'-diisothiocyanatostilbene-2,2'disulfonic acid) or IAA-94 (an indanyloxyacetic acid) inhibited the outward rectifier but did not a&t the low-conductance channel or CAMP-stimulated transepithelial current. These results suggest the low-conductance Cl channel may contribute to apical membrane conductance during CAMP-stimulated secretion.

Volume‐activated Cl− secretion and transepithelial vinblastine secretion mediated by P‐glycoprotein are not correlated in cultured human T84 intestinal epithelial layers

“…The CI-secretion stimulated by cell-swelling, reported here, is blocked by extraceilular DIDS, in contrast to the VIP-stimulated CI" secretion (mediated by CFTR), which is unaffected by this agent [2,5]. The volume-stimulated CI-secretion is unaffected by 100 /~NI DiD-forskolin, in contrast to the data obtained for the volume-activated CI-conductance in MDRl.transletted cell lines [1].…”

“…Epithelial monolayers of T~ human colonic adenocarcinoma cells express both CFTR [3] and MDR1 [4] and this is associated with cAMP-stimulated transepithelial CI-secretion [2,5] and transepithelial vinblastine secretion [4], respectively. P-glycoprotein is expressed in the apical poles of intestinal enterocytes [6] and the existence of polarised secretion of vinblastine by intact T~ monolayers is consistent with its iocalisation within the apical membrane [4].…”

“…The increased SCC is quantitatively accounted for by an increased electrogenic CI" secretion [10]. The small conductance (5-10 pS)cAMP-activated el-channel which is insensitive to inhibition by the stilbene 4,4'-diisothiocyanantostilbene-2,2'-disulphonic acid (DIDS) accounts for the substantive portion of the cAMP-induced Cl-current in T~ cells [2,7]; the cAMPstimulated SCC in intact T~ epithelia (Ci-secretion) is also insensitive ~'.o DIDS inhibition [5]. The most-studied Cl-channel in epithelial cells is the outward rectifier (30-50 pS) [7,11].…”

Characterization of cAMP dependent CFTR‐chloride channels in human trache gland cells

“…The deactivated excised channel could not be reactivated by pulsing the voltage to high positive or negative values. Cl-selective channels found in immortalized airway cell lines [ 181, human pancreatic duct [30], thyroid [31] and T84 cells [32]. Expression of the cystic fibrosis gene produced a CAMP-regulated Cl-channel with a cell-attached conductance of 8 pS in the nonepithelial Sf9 cells [6], 4 pS in Vero cells [9], 9 pS in CHO cells [8] and 10 pS in HeLa cells [7].…”

Concomitant activation of Cl‐ and K+ currents by secretory stimulation in human epithelial cells.

“…channels affected in cystic fibrosis have previously been reported (Tabcharani et al 1990). We used Torskolin, an agonist of adenylyl cyclase, to increase intracellular cAMP.…”