Calcium dependence of integrity of the actin cytoskeleton of
proximal tubule cell microvilli.
Sogabe, Keizo, Nancy F. Roeser, Julie A. Davis, Saul Nurko, Manjeri A.
Venkatachalam, and Joel M. Weinberg.
Division of Nephrology, Department of Internal Medicine, University
of Michigan and Veteran's Administration Medical Center, Ann Arbor,
Michigan, 48109 and Departments of Pathology and Medicine, The
University of Texas Health Science Center at San Antonio, San
Antonio, Texas, 78284
APStracts 3:0052F, 1996.
To better define the role of Ca2+ in pathophysiological alterations of
the proximal tubule microvillus actin cytoskeleton, we studied
freshly isolated tubules in which intracellular free Ca2+ was
equilibrated with highly buffered, precisely defined medium Ca2+
levels using a combination of the metabolic inhibitor, antimycin, and
the ionophore, ionomycin, in the presence of glycine to prevent
lethal membrane damage and resulting nonspecific changes. Increases
of Ca2+ to > 10 [mu]M were sufficient to initiate concurrent
actin depolymerization, fragmentation of F-actin into forms requiring
high speed centrifugation for recovery, redistribution of villin to
sedimentable fractions and structural microvillar damage consisting
of severe swelling and fragmentation of actin cores. These
observations implicate Ca2+-dependent, villin-mediated actin
cytoskeletal disruption in tubule cell microvillar damage under
conditions conceivably present during pathophysiological states.
However, despite prior evidence for cytosolic free Ca2+ increases of
the same order of magnitude and similar structural microvillar
alterations, Ca2+ and villin mediated events did not appear to
account for the initial microvillar damage that occurs during ATP
depletion induced by antimycin alone or hypoxia.
Received 7 September 1995; accepted in final form 1 March 1996.
APS Manuscript Number F300-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 27 March 96