Photobleaching through glass micropipettes

Sodium channels without lateral mobility in the sarcolemma of frog skeletal muscle

W. Stuhmer, Wolfhard Almers

Research output: Contribution to journalArticle

47 Citations (Scopus)

Abstract

Sodium currents were recorded from frog skeletal muscle by using fire-polished micropipettes to electrically isolate and voltage clamp a small patch of sarcolemma. Sodium current amplitude served as an assay for the number of functional sodium channels in the patch. With the pipette as a light guide, these channels were irradiated with ultraviolet (UV) light directed through a quartz fiber into the back end of the pipette. The UV light emerging from the pipette tip caused localized destruction of the sodium channels in the patch, reducing sodium current 3- to 5-fold during a 30-90 s irradiation. If sodium channels could diffuse laterally in the membrane, current from the patch should recover with time as fresh channels enter from neighboring areas. No such recovery was observed during observation for 1 hr after irradiation. Our results set an upper limit of 10-11 cm2/s for the diffusion coefficient - 1/1000th that of rhodopsin, a membrane protein in the cell membrane of retinal rods. It is suggested that sodium channels are anchored in the sarcolemma.

Original languageEnglish (US)
Pages (from-to)946-950
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume79
Issue number3 I
StatePublished - 1982
Externally publishedYes

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Photobleaching
Sarcolemma
Sodium Channels
Anura
Glass
Skeletal Muscle
Sodium
Ultraviolet Rays
Membrane Proteins
Retinal Rod Photoreceptor Cells
Quartz
Rhodopsin
Observation
Light
Membranes

ASJC Scopus subject areas

  • General
  • Genetics

Cite this

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abstract = "Sodium currents were recorded from frog skeletal muscle by using fire-polished micropipettes to electrically isolate and voltage clamp a small patch of sarcolemma. Sodium current amplitude served as an assay for the number of functional sodium channels in the patch. With the pipette as a light guide, these channels were irradiated with ultraviolet (UV) light directed through a quartz fiber into the back end of the pipette. The UV light emerging from the pipette tip caused localized destruction of the sodium channels in the patch, reducing sodium current 3- to 5-fold during a 30-90 s irradiation. If sodium channels could diffuse laterally in the membrane, current from the patch should recover with time as fresh channels enter from neighboring areas. No such recovery was observed during observation for 1 hr after irradiation. Our results set an upper limit of 10-11 cm2/s for the diffusion coefficient - 1/1000th that of rhodopsin, a membrane protein in the cell membrane of retinal rods. It is suggested that sodium channels are anchored in the sarcolemma.",
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