Calcium in epithelial cell contraction

Abstract

Epithelial morphogenesis in many organs involves asymmetric microfilamentmediated cellular contractions. Similar contractions, in terms ofultrastructure and cytochalasin B sensitivity, can be induced in the carcinoma cell line C-411 in culture. This line was used to compare total intracellular calcium levels ([Cali) 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 µg Ca/mg protein in early confluent cultures, and from 0.3 to 1.0-2.0 µg 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°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 × 10-4 M), and D-600 (1.0-2.0 x 10-4 M). The Ca ionophore A23187 had no effect at 5.0 × 10-6 M and was inhibitory at higher concentrations. The results provide direct evidence for increased [Cali in contracting epithelial cells, and suggest that Ca influx is required for such contraction to take place. © 1980, Rockefeller University Press., All rights reserved.