TY - JOUR
AU - Dietl, Paul
AB - 1 Using conventional microelectrodes, the perforated patch clamp technique and fluorescence microscopy with fura‐2, we investigated the relationship between the cell membrane potential, whole‐cell currents and the free cytoplasmic Ca2+ concentration ((Ca2+)i) in response to 10 nM endothelin‐1 (ET) in a rat respiratory epithelial cell line (L2). 2 Microelectrode experiments revealed that ET caused an immediate depolarization of the cell membrane potential (Vm) by 25 mV, which was unaffected by Na+ replacement with N‐methyl‐D‐glucamine+ (NMDG+) or by omission of bath Ca2+. In contrast, ET depolarized the cells by 61 mV in the presence of low Cl− (6 mM), resulting in a complete breakdown of Vm. 3 In perforated patch clamp experiments, the ET‐induced whole‐cell current (IET) exhibited a slight outward rectification with a reversal potential (Vrev) of ‐22·7 mV. IET was reduced by 85 % in low Cl− (6 mM), but was unaffected by Ca2+ removal, Na+ replacement with NMDG+, pipette K+ replacement with Cs+ or 1 mM Ni2+ in the bath. 4 I ET was unaffected by (+)‐isradipine (100 nM), a specific L‐type Ca2+ channel (L‐VDCC) blocker. Transient inward Sr2+ currents through L‐VDCCs were blocked by ET. 5 ET induced a biphasic Ca2+ signal, consisting of a ‘peak’ and a ‘plateau’ elevation of (Ca2+)i. Simultaneous patch clamp and fura‐2 measurements revealed that IET coincided with intracellular Ca2+ release but clearly outlasted the elevation of (Ca2+)i. When the rise of (Ca2+)i was prevented by pretreatment with thapsigargin in a Ca2+‐free bath, both activation time and amplitude of IET were reduced. Under these conditions, ET caused a decrease of (Ca2+)i. 6 The Cl− channel blocker mefenamic acid (MFA) had a dual, concentration‐dependent effect on both IET and the ET‐induced ‘plateau’ elevation of (Ca2+)i: an increase at 10 μM, but an almost complete block at 100 μM. The effect of MFA on IET preceded the effect on (Ca2+)i. 7 The ET‐induced ‘plateau’(Ca2+)i fell below control values in a low‐Cl− (6 mM) solution. 8 These data indicate an amplifying function of intracellular Ca2+ release on an otherwise Ca2+‐independent, unique Cl− current by ET. Moreover, this Cl− current appears to be functionally coupled with dihydropyridine (DHP)‐insensitive Ca2+ entry, suggesting a modulatory role for long‐lasting effects of ET.
TI - Long‐term induction of a unique Cl − current by endothelin‐1 in an epithelial cell line from rat lung: evidence for regulation of cytoplasmic calcium
JF - The Journal of Physiology
DO - 10.1111/j.1469-7793.1998.055bi.x
DA - 1998-08-01
UR - https://www.deepdyve.com/lp/wiley/long-term-induction-of-a-unique-cl-current-by-endothelin-1-in-an-CcoGiBKx7N
SP - 55
VL - 511
IS - 1
DP - DeepDyve
ER -