AJP - Cell Physiology, Vol 252, Issue 4 C418-C427, Copyright © 1987 by American Physiological Society
Ca2+ and MgATP2- dependence of shortening in skinned single smooth muscle cells
D. M. Warshaw, W. J. McBride and M. S. Hubbard
Most studies of skinned smooth muscle have been performed in whole tissue
preparations. In this study, we report the development of a chemically
skinned single smooth muscle cell preparation from the toad, Bufo marinus,
stomach. Isolated smooth muscle cells were skinned using saponin. The
effect of various ionic environments (i.e., changing free Ca2+ and MgATP2-)
on skinned cell contractile response was assessed by measuring cell lengths
from populations of cells using a computer-assisted length-measuring
system. Comparison of cell length histograms were used to determine the
extent of cell shortening in response to a given ionic perturbation. Once
skinned, the single cells shortened with a sensitivity to free calcium
(ED50 = 1.5 microM Ca2+) that was three orders of magnitude lower than
potassium depolarized cells (ED50 = 1.5 mM Ca2+). In addition to the
calcium sensitivity, the effect of free MgATP2- on the extent of cell
shortening was investigated. The extent of cell shortening was dependent on
free MgATP2- with the maximum shortening response occurring at MgATP2-
greater than 1 mM.
