The Journal of Cell Biology, Vol 85, 325-336, Copyright © 1980 by The Rockefeller University Press
Calcium in epithelial cell contraction
HC Lee and N Auersperg
Epithelial morphogenesis in many organs involves asymmetric
microfilament-mediated cellular contractions. Similar contractions, in
terms of ultrastructure and cytochalasin B sensitivity, can be induced in
the carcinoma cell line C-4II in culture. This line was used to compare
total intracellular calcium levels ([Ca]i) in contracted monolayer
fragments and in control cultures, and to determine whether epithelial cell
contraction depends on influx of extracellular Ca. [Ca]i, defined as Ca not
displaceable by lanthanum, was measured by atomic absorption
spectrophotometry. Degrees of contraction were determined from shape
changes of monolayer fragments. Detachment from the growth surface
initiated cellular contractions and caused an immediate increase in [Ca]i,
from 1.0 to 4.0-5.0 micrograms Ca/mg protein in early confluent cultures,
and from 0.3 to 1.0-2.0 micrograms Ca/mg protein in crowded cultures. This
increase was followed by a gradual decline in [Ca]i, though Ca levels
remained higher than in controls and contraction progressed for 30 min.
Contraction was inhibited completely by cold (7 degrees C) and by Ca-free
medium, and in a dose-dependent manner by papaverine (2.5 x 10(-6) M-2.5 x
10(-4) M), lanthanum (1.0 x 10(-6) M-1.0 x 10(-4) M); and D-600 (1.0-2.0 x
10(- 4) M). The Ca ionophore A23187 had no effect at 5.0 x 10(-6) M and was
inhibitory at higher concentrations. The results provided direct evidence
for increased [Ca]i in contracting epithelial cells, and suggest that Ca
influx is required for such contraction to take place.
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