Hypoxia induces changes in phospholipase a2 in rat proximal
tubules: evidence for multiple forms .
Choi, Kyo Hun, Charles L. Edelstein, Patricia Gengaro, Robert W.
Schrier, and Raphael A. Nemenoff.
Division of Renal Diseases and Hypertension, Department of
Medicine, University of Colorado School of Medicine, Denver, Colorado
80262
APStracts 2:0114F, 1995.
Increased free fatty release during hypoxia is believed to contribute
to cell injury. This phenomenon is likely to be mediated through
activation of specific isoforms of phospholipase A2 (PLA2). In this
study, PLA2 enzymatic activity was measured in cell-free extracts
prepared from rat renal proximal tubules. Both soluble and membrane
-associated PLA2 activity were detected. All PLA2 activity detected
during normoxia was Ca2+-dependent. Fractionation of cytosolic
extracts by gel filtration revealed three peaks of PLA2 activity.
Exposure of tubules to hypoxia resulted in stable activation of
soluble PLA2 activity, which correlated with disappearance of the
highest molecular weight form (>100 kDa) and appearance of a low
molecular weight form (15 kDa) of PLA2. Hypoxia also resulted in
release of a low-molecular weight form of PLA2 into the extracellular
media. Pre-treatment of tubules with glycine prior to hypoxia blocked
this release of PLA2, but not activation of soluble PLA2 activity.
These studies provide direct evidence for PLA2 activation during
hypoxia, and suggest that multiple mechanisms regulate free fatty
acid release associated with hypoxic injury.
Received 22 March 1995; accepted in final form 27 June 1995.
APS Manuscript Number F98-5.
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.