ISSN:
1432-1424
Keywords:
trachea
;
epithelium
;
channel
;
NPPB
;
gating
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary 5-Nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) has been shown to produce a reduction in channel open probabilty i n a number of epithelial chloride channels. We have investigated its action on a calcium-dependent airway epithelial chloride channel, which shows voltage-dependent gating following incorporation into planar phospholipid bilayers. Since the channel demonstrates a distinct subconductance state at approximately one-third of the fully open level, both 50 and 20% threshold analysis (TA) have been used to describe channel kinetics. Lifetime analysis using 50% TA in the absence of NPPB showed that two open and three closed lifetimes provided the optimal fit. Similar analysis using 20% TA required only two closed lifetimes and allowed for tentative assignment of tau values to either substate or fully closed events. NPPB (10–100 μm) produced a concentration-related shift of the normal voltage dependence of gating, with more negative holding potentials being required to produce a given channel open probability than in the absence of NPPB. Ten μM NPPB produced a similar shift in lifetime values. However, addition of 50 μm NPPB produced a unique, single open lifetime. No evidence was found for NPPB acting as a direct voltage-dependent blocker of chloride conductance.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00231887
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