Ultrastructural Changes in Murine Leukemia Cells Exposedto L-Asparaginasein Vitro

Abstract

Ultrastructural changes in a sensitive murine leukemia cell line (L5178Y) exposed to L-asparaginase in vitro are described. During the first four hours, cytoplasmic changes included dilatation of granular endoplasmic reticulum and swelling of mitochondria. A few cells showed damage of the nuclear envelope. After exposure for 24 hr. to two different concentrations of L-asparaginase, nuclear changes were evident in addition to cytoplasmic changes. These included patchy or total loss of the nuclear envelope, usually accompanied by dilatation of the perinuclear endoplasmic reticulum. Desegregation of nucleoplasm was also observed. Although the observed cellular changes could not be considered specific for L-asparaginase effect, they are probably sufficient to interfere with the viability of sensitive leukemic cells. In view of the relative absence of these changes in the control cells, it is perhaps permissible to suggest that these morphologic alterations may explain the antitumor property of L-asparaginase.