AJP - Cell Physiology, Vol 263, Issue 5 C995-1000, Copyright © 1992 by American Physiological Society
Effect of cytochalasin D on the actin cytoskeleton of the toad bladder epithelial cell
N. Franki, G. Ding, Y. Gao and R. M. Hays
Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461.
Cytochalasins are widely used to determine the role of actin in cellular
processes. Their actions include capping of the barbed end of actin
filaments as well as dimer formation, nucleation, and polymerization. We
determined the effect of cytochalasin D (CD) on F-actin in the toad urinary
bladder, an epithelium in which vasopressin depolymerizes F-actin. At a low
concentration (0.25 microM), CD depolymerized F-actin in the unstimulated
cell; at higher concentrations, there was a progressive reduction of
depolymerization until actual polymerization was seen. Vasopressin plus CD
produced no greater depolymerization than vasopressin alone, suggesting
that CD and vasopressin act to a large extent on the same pool of F-actin.
CD plus vasopressin also enhanced the fusion rate of aggrephores compared
with vasopressin alone, indicating that intact actin filaments retard
aggrephore fusion. Despite the increase in aggrephore fusion, water flow
was not enhanced by CD, confirming previous reports that intact actin
filaments are required for water channel emergence or stabilization in the
apical membrane. Vasopressin plus 1 microM CD produced a striking increase
in microvillar length, direct evidence of the polymerizing action of CD in
the cell.
