ISSN:
1432-1424
Keywords:
Anion current
;
NPPB
;
DIDS
;
Furosemide
;
Whole-cell patch clamp
;
Sheep parotid
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract Previous studies have shown that the whole-cell current-voltage (I-V) relation of unstimulated sheep parotid cells is dominated by two K+ conductances, one outwardly and the other inwardly rectifying. We now show that once these K+ conductances are blocked by replacement of pipette K+ with Na+ and by the addition of 5 mmol/liter CsCl to the bath, there remains an outwardly rectifying conductance with a reversal potential of 0 mV. Replacement of 120 mmol/liter NaCl in the pipette solution with an equimolar amount of Na-glutamate shifted the reversal potential of this residual current to -55 mV, indicating that the conductance was Cl− selective. The Cl− current was activated by increasing the free Ca2+ in the pipette solution from 10 to 100 nmol/liter. When the Ca2+ concentration in the pipette solution was 10 nmol/liter, the relaxations observed in response to membrane depolarization could be fitted with a single exponential, whose time constant increased from 81 to 183 ms as the pipette potential was increased from -30 to +60 mV. Relaxation analysis showed that the current was activated by membrane depolarization. Reversal potential measurements in experiments in which external Cl− was replaced with various anions, gave the following relative permeabilities: SCN- (1.80) 〉 I- (1.09) 〉 CI- (1) 〉 NO 3 - (0.92) 〉 Br- (0.75). The relative conductances were: SCN- (2.18) 〉 I- (1.07) 〉 Cl− (1.00) 〉 Br- (0.91) 〉 NO 3 - (0.50). The Cl− current was blocked by NPPB (ID50 ≈ 10 μm), DIDS (10 or 30 μmol/liter) and furosemide (100 μmol/liter).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00211098
