Characterisation of cell volume loss in cem-c7a cells during
dexamethasone-induced apoptosis.
Benson, R. S. P., S. Heer, C. Dive, and A. J. M Watson.
Depts of Medicine and School of Biological Sciences, University of
Manchester, Manchester M13 9PT, ENGLAND
APStracts 2:0363C, 1995.
A reduction in cell volume is a fundamental feature of apoptosis. We
have characterised changes in cell volume, together with nuclear
changes, occurring in dexamethasone-induced apoptosis in CEM-C7A
lymphoblastoid cells. Cell volume was measured by electronic cell
sizing and flow cytometry and two distinct phases of volume loss were
observed. The first phase began 12 hours after addition of
dexamethasone (5[mu]M) and progressed until 36 hours when chromatin
condensation was detected in intact cells. Removal of dexamethasone
before 36 hours (the pre-commitment period), resulted in reversal of
the volume decrease and prevented the appearance of nuclear changes.
Cell shrinkage in the first 24 hours of dexamethasone exposure, was
associated with a net loss of potassium but no change in cellular
buoyant density. There were no significant differences in the rates
of volume recovery after either hypertonic or hypotonic stimuli.
These observations favour a mechanism of cell shrinkage involving
loss of the entire cytoplasmic contents, possibly following
proteolysis, rather than loss of only osmolytes and water. The second
phase of volume loss was coincident with chromatin condensation and
was associated with cellular fragmentation and a reduction in
cellular density. We conclude that volume loss in this model of
apoptosis is mediated by multiple mechanisms which are both dependent
and independent of cellular fragmentation.
Received 2 May 1995; accepted in final form 25 September 1995.
APS Manuscript Number C241-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95