Document Detail

Some properties of acetylcholine receptors in human cultured myotubes.
MedLine Citation:
PMID:  2408280     Owner:  NLM     Status:  MEDLINE    
The distribution and single channel properties of acetylcholine (ACh) receptors in human myotubes grown in tissue culture have been examined. Radioautography of myotubes labelled with [125I]alpha-bungarotoxin showed that ACh receptors are distributed uniformly over the myotube surface at a density of 3.9 +/- 0.5 receptors per square micrometre. Accumulations of ACh receptors (hot spots) were found rarely. The conductance and kinetics of ACh-activated channels were investigated with the patch-clamp technique. Cell-attached membrane patches were used in all experiments. A single channel conductance in the range 40-45 pS was calculated. No sublevels of conductance (substates) of the activated channel were observed. The distribution of channel open-times varied with ACh concentration. With 100 nM ACh, the distribution was best fitted by the sum of two exponentials, whereas with 1 microM ACh a single exponential could be fitted. The mean channel open-time at the myotube resting potential (ca. -70 mV, 22 degrees C) was 8.2 ms. The distribution of channel closed-times was complex at all concentrations of ACh studied (100 nM to 10 microM). With desensitizing doses of ACh (10 microM), channel openings occurred in obvious bursts; each burst usually appeared as part of a 'cluster' of bursts. Both burst duration and mean interval between bursts increased with membrane hyperpolarization. Individual channel open-times and burst durations showed similar voltage dependence (e-fold increase per 80 mV hyperpolarization), whereas both the channel closed-times within a burst and the number of openings per burst were independent of membrane potential.
D J Adams; S Bevan
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Proceedings of the Royal Society of London. Series B, Containing papers of a Biological character. Royal Society (Great Britain)     Volume:  224     ISSN:  0080-4649     ISO Abbreviation:  Proc. R. Soc. Lond., B, Biol. Sci.     Publication Date:  1985 Apr 
Date Detail:
Created Date:  1985-06-26     Completed Date:  1985-06-26     Revised Date:  2007-04-30    
Medline Journal Info:
Nlm Unique ID:  7505889     Medline TA:  Proc R Soc Lond B Biol Sci     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  183-96     Citation Subset:  IM    
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MeSH Terms
Acetylcholine / physiology
Cell Compartmentation
Cells, Cultured
Electric Conductivity
Ion Channels / physiology
Membrane Potentials
Muscles / physiology,  ultrastructure
Receptors, Cholinergic / physiology*
Sarcolemma / physiology*,  ultrastructure
Reg. No./Substance:
0/Ion Channels; 0/Receptors, Cholinergic; 51-84-3/Acetylcholine

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