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Lateral distribution of sodium and potassium channels in frog skeletal muscle: measurements with a patch‐clamp technique.
Author(s) -
Almers W,
Stanfield P R,
Stühmer W
Publication year - 1983
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1983.sp014580
Subject(s) - sarcolemma , chemistry , pipette , potassium , sodium channel , anatomy , materials science , amplitude , sodium , analytical chemistry (journal) , molecular physics , biophysics , optics , skeletal muscle , physics , biology , organic chemistry , chromatography
We describe a method for recording Na+ and K+ currents (INa and IK) from small, voltage‐clamped patches of sarcolemma by means of fire‐polished glass micropipettes of 7‐15 microns tip diameter. Recordings can be made successively from many areas of one fibre. On a given fibre, the amplitudes of INa and IK varied from point to point. Maximum Na+ current densities varied up to three‐fold over distances of 10‐30 microns, typically between 4 and 12 mA/cm2. K+ currents showed somewhat less lateral variation. Local densities of INa and IK showed no correlation. Apparently the density of Na+ (and, to a lesser extent, K+) channels varies laterally. A contour map of Na+ channel density is constructed for a 20 microns X 90 microns section of sarcolemma. Based on the steepness of lateral gradients in channel density and the estimated survival time of a Na+ channel, it is calculated that at least half of the Na+ channels have a lateral diffusion coefficient of less than 2 X 10(‐12) cm2/s. This is three orders of magnitudes less than expected from their molecular size, and suggests that these channels are anchored in the sarcolemma.