CELL SHRINKAGE DURING APOPTOSIS IS NOT OBLIGATORY.
APOPTOSIS OF U937 CELLS INDUCED BY STAUROSPORINE AND ETOPOSIDE
A. A. Vereninov, T. S. Goryachaya, V. V. Matveev, A. V. Moshkov,
Yu. M. Rozanov, G. A. Sakuta, A. V. Shirokova, V. E. Yurinskaya
Institute of Cytology RAS, St. Petersburg, Russia;
e-mail: veren@mail.cytspb.rssi.ru
A study was made of apoptotic cell shrinkage, which is generally believed to be a hallmark of apoptosis. The two
conventional models of apoptosis were used for examination of changes in cell water balance - one is apoptosis caused in human
lymphoma cell line U937 by staurosporine, and the other by etoposide. Intracellular water was determined by measuring buoyant density
of cells in continuous Percoll gradient. Apoptosis was recognized by microscopy and flow cytometry. Apoptosis caused by staurosporine
(1 μM, 4 h) was found to be associated with a decrease in cell water content by almost 24 %. In contrast, no decrease in cell water content
was observed in U937 cells incubated with etoposide (50 μM, 4 h), in spite of the number of features suggesting the presence of apoptosis,
such as the appearance of apoptotic bodies, chromatin condensation and fragmentation and disappearance of S-phase cells in DNA
histogram. It is concluded that definition of apoptosis as "shrinkage-necrosis" (Kerr, 1971) needs correcting: the distinction of apoptotic
cells involves the absence of swelling, rather than cell shrinkage.
Key words: apoptosis, cell water, etoposide, staurosporine, cell shrinkage, apoptotic volume
decrease
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