AJP - Cell Physiology, Vol 256, Issue 2 C434-C440, Copyright © 1989 by American Physiological Society
Patch clamp of sarcolemmal spheres from stretched skeletal muscle fibers
P. Stein and P. Palade
Department of Physiology and Biophysics, University of Texas Medical Branch, Galveston 77550.
Stretching frog skeletal muscle fibers to the breaking point results in the
rapid formation of numerous large spheres of membrane (5-80 microns diam).
The surface of the spheres readily forms gigaohm (G omega) seals against
patch pipettes, allowing low-noise single-channel recording. Currents
recorded from patches isolated from these spheres indicate that they
contain a variety of channels including 1) a small Na+-selective channel
seen in the presence of veratridine, 2) a K+-selective channel which is
blocked by millimolar Mg-ATP, and 3) a relatively large voltage-dependent
Cl- channel which is blocked by Zn2+ and limited in selectivity over other
anions [PCl/PMOPS = 3.7; MOPS, 3-(N-morpholino)propanesulfonic acid]. These
channels have been described previously and have been identified as markers
for sarcolemmal (SL) membrane. Accordingly, this method allows rapid and
direct recording of channels in the SL membrane without first having to
pretreat fibers with proteolytic enzymes to render the SL accessible to
patch pipettes.
