Morphological and cytogenetical changes in HR-18 rat ascites cells after in vitro 3-[bis(2-chloroethyl)amino]-4-methylbenzoic acid (NSC-146171; IOB-82) administration.

A bifunctional alkylating agent, 3-[Bis(2-chloroethyl) amino]-4-methylbenzoic acid (NSC-146171; IOB-82) was administered in HR-18 rat ascites cell cultures (which presented 2 morphologic cellular types: A and B type cells, genetically, 2 cellular populations having 41-45 and 85-86 chromosomes and cells with high ploidy), and the morphological and cytogenetical effects were related to the compound concentration. Thus, 24 h after IOB-82 administration in small doses (3.62 X 10(-4) micron/ml), important morphological changes were observed: nuclear changes (denuded nuclei, pyknosis) and cytoplasmic alterations (breaks at the exoplasm level, followed by cytoplasmic extrusions in extracellular spaces, cytoplasmic vacuolization). In addition to these changes, other abnormalities were observed when IOB-82 was administered in large doses (3.62 X 10(-3) micron/ml), i.e., nuclear changes (nuclear residues, granulation of the nuclear material and spreading of the nuclear content into cytoplasm) and cytoplasmic alterations (cytoplasmic shades and accentuated cytoplasmic vacuolization). Generally, the large A-type cells were more affected. Twenty-four h after IOB-82 treatment (with small or large doses), the chromatid and chromosome aberrations (gaps, breaks, deletions, fragments) were also observed. These aberrations were more numerous when IOB-82 was administered in large doses. Both morphological and cytogenetical changes indicate that the effect of IOB-82 could be radiomimetic. Changes produced and their incidence appear to depend on the concentration of IOB-82 employed and the morphological type of ascites cells. These are expressed in terms of multiple abnormality production in these cells. IOB-82 treatment produced changes in chromosome numbers and especially the disappearance of polyploid cells and cell populations with 85-86 chromosomes. These results indicate a possible correlation between the increased sensitivity of HR-18 rat ascites cells and changes in ploidy.