ISSN:
1432-2013
Keywords:
Cl− conductance
;
K+ conductance
;
ATP
;
Bradykinin
;
Histamine
;
Bronchial epithelial cells
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The present study was performed to examine Ca2+-dependent and cell-swelling-induced ion conductances in a polarized bronchial epithelial cell line (16HBE14o-). Whole-cell currents were measured in fast and slow whole-cell patch-clamp experiments in cells grown either on filters or on coated plastic dishes. In addition the transepithelial voltage (V te) and resistance (R te) were measured in confluent monolayers. Resting cells had a membrane voltage (V m) of −36±1.1 mV (n=137) which was mainly caused by K+ and Cl− conductances and to a lesser extent by a Na+ conductance. V te was apical-side-negative after stimulation. Equivalent short-circuit current (I sc = V te/R te) was increased by the secretagogues histamine (0.1 mmol/l), bradykinin (0.1–10 μmol/l) and ATP (0.1–100 μmol/l). The histamine-induced I sc was blocked by either basolateral diphenhydramine (0.1 mmol/l, n=4) or apical cimetidine (0.1 mmol/l, n=4). In fast and slow whole-cell recordings ATP and bradykinin primarily activated a transient K+ conductance and hyperpolarized V m. This effect was mimicked by the Ca2+ ionophore ionomycin (1 μmol/l, n=11). Inhibition of the bradykinin-induced I sc by the blocker HOE140 (1 μmol/l, n=3) suggested the presence of a BK2 receptor. The potency sequence of different nucleotide agonists on the purinergic receptor was UTP ≈ ATP 〉 ITP 〉 GTP ≈ CTP ≈ [β,γ-methylene] ATP ≈ 2-methylthio-ATP = 0 and was obtained in I sc measurements and patch-clamp recordings. This suggests the presence of a P2u receptor. Hypotonic cell swelling activated both Cl− and K+ conductances. The Cl− conductance was only slightly inhibited by 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (0.5 mmol/ l, n=3). These data indicate that 16HBE140- bronchial epithelial cells, which are known to express high levels of cystic fibrosis transmembrane conductance regulator protein, form a secretory epithelium. While hypotonic cell swelling activates both K+ and Cl− channels, the Ca2+-induced Cl− secretion is due mainly to activation of basolateral K+ channels.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00374583
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