Contribution of actin cytoskeletal alterations to atp depletion and
calcium-induced proximal tubule cell injury.
Nurko, Saul, Keizo Sogabe, Julie A. Davis, Nancy F. Roeser, Michael
Defrain, Alexander Chien, Daniel Hinshaw, Brian Athey, Walter
Meixner, Manjeri A. Venkatachalam, and Joel M. Weinberg.
Division of Nephrology, Department of Internal Medicine, Department
of Surgery, and Department of Anatomy and Cell Biology, 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 2:0117F, 1995.
The actin cytoskeleton of rabbit proximal tubules was assessed by
deoxyribonuclease (DNase) binding, sedimentability of detergent
-insoluble actin, laser scanning confocal microscopy, and
ultrastructure during exposure to hypoxia, antimycin, or antimycin
plus ionomycin. One third of total actin was DNase-reactive in
control cells prior to deliberate depolymerization and a similar
proportion was unsedimentable from detergent lysates during 2.5 hr at
100,000 g. Tubules injured by hypoxia or antimycin alone without
glycine showed Ca2+-dependent pathology of the cytoskeleton
consisting of increases in DNase-reactive actin, redistribution of
pelletable actin, and loss of microvilli concurrent with lethal
membrane damage. In contrast, tubules similarly depleted of ATP and
incubated with glycine showed no significant changes of DNase
-reactive actin or actin sedimentability for up to 60 min., but
nevertheless developed substantial loss of basal membrane-associated
actin within 15 min. and disruption of actin cores and clubbing of
microvilli at durations greater than 30 min. These structural changes
that occurred in the presence of glycine were not prevented by
limiting Ca2+ availability or pH 6.9. Very rapid and extensive
cytoskeletal disruption followed antimycin plus ionomycin treatment.
In this setting, glycine and pH 6.9 decreased lethal membrane damage,
but did not ameliorate pathology in the cytoskeleton or microvilli;
limiting Ca2+ availability partially protected the cytoskeleton but
did not prevent lethal membrane damage. The data suggest that both
ATP depletion-dependent, but Ca2+-independent as well as Ca2+
-mediated processes can disrupt the actin cytoskeleton during acute
proximal tubule cell injury, that both types of change occur despite
protection afforded by glycine and reduced pH against lethal membrane
damage, and that Ca2+-independent processes primarily account for
prelethal actin cytoskeletal alterations during simple ATP depletion
of proximal tubule cells.
Received 18 May 1995; accepted in final form 20 June 1995.
APS Manuscript Number F158-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.