Ca(2+)- and swelling-induced activation of ion conductances in bronchial epithelial cells.
The present study was performed to examine Ca(2+)-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 (Vte) and resistance (Rte) were measured in confluent monolayers. Resting cells had a membrane voltage (Vm) 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. Vte was apical-side-negative after stimulation. Equivalent short-circuit (Isc = Vte/Rte) was increased by the secretagogues histamine (0.1 mmol/l), bradykinin (0.1 - 10 mumol/l). and ATP (0.1 - mumol/l). The histamine-induced Is 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 Vm. This effect was mimicked by the Ca2+ ionophore ionomycin (1 mumol/l, n = 11). Inhibition of the bradykinin-induced Isc by the blocker HOE140 (1 mumol/l, n = 3) suggested the presence of a BK2 receptor. The potency sequence of different nucleotide agonists on the purinergic receptor was UTP approximately ATP > ITP > GTP approximately CTP approximately [beta, gamma-methylene] ATP approximately 2-methylthio-ATP = 0 and was obtained in Isc measurements and patch-clamp recordings. This suggests the presence of a P2u receptor. Hypotonic cell swelling activated both Cl- and K+ conductances.(ABSTRACT TRUNCATED AT 250 WORDS)
Koslowsky
T
T
Physiologisches Institut, Albert-Ludwigs-Universität Freiburg, Germany.
Hug
T
T
Ecke
D
D
Klein
P
P
Greger
R
R
Gruenert
D C
DC
Kunzelmann
K
K
D000255:Adenosine Triphosphate / Q000494:pharmacology; D001920:Bradykinin / Q000494:pharmacology; D001980:Bronchi / Q000502:physiology*; D002118:Calcium / Q000502:physiology*; D002460:Cell Line; D004553:Electric Conductivity; D004848:Epithelium; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D007477:Ions
D007477:Ions; D015759:Ionomycin; D000255:Adenosine Triphosphate; D001920:Bradykinin; D002118:Calcium