Ultrastructural nucleolar alterations induced by an ametantrone–poly r(A-U) complex.

Ultrastructural nucleolar alterations induced by an ametantrone–poly r(A-U) complex.

Jamison J M; Gilloteaux J; Thiry M; Authelet M; Goessens G; Summers J L

Tissue & cell

1998

1998-08

The current study has documented changes in the ultrastructure as well as in the intranucleolar distribution of rDNA and rRNA in RT4 (human transitional cell bladder carcinoma) cell nucleoli following a 3-h exposure to toxic doses of 50 microM ametantrone (AMT), 200 microM poly (adenylate-uridylate) (poly r(A-U) or an AMT/poly r(A-U) combination with an AMT/polyribonucleotide ratio of 1:4 and a poly r(A-U) concentration of 200 microM. While the main nucleolar components (fibrillar center (F), dense fibrillar component (D), granular component (G) and interstices (I) can be discerned following all treatments, the nucleoli exhibit: compaction, segregation, a decrease in the number of F, an increase in the size of remaining F, margination of intranucleolar chromatin and retention of intranucleolar pre-rRNA and rRNA. The relative abilities of the test agents to induce nucleolar compaction are AMT/poly r(A-U) \textgreater poly r(A-U) \textgreater AMT \textgreater sham-treated, while the abilities of the test agents to induce the remaining nucleolar changes are AMT/poly r(A-U) \textgreater or = AMT \textgreater poly r(A-U) \textgreater sham-treated cells. Poly r(A-U) and the induced interferon induce nucleolar compaction, while AMT produces nucleolar segregation. These results are consistent with a model in which the poly r(A-U) and/or the AMT inhibit DNA transcription and rRNA processing as well as the release of nascent preribosomes from the nucleolus.

Antineoplastic Agents/*pharmacology; Carcinoma; Cell Nucleolus/*chemistry/drug effects/ultrastructure; Cultured/chemistry/drug effects/ultrastructure; DNA; Humans; Immunoelectron; Microscopy; Mitoxantrone/*analogs & derivatives/pharmacology; Neoplasm/*analysis; Neoplasm/analysis; Poly A-U/*pharmacology; Ribosomal/analysis; Ribosomal/analysis/ultrastructure; RNA; Transitional Cell; Tumor Cells; Urinary Bladder Neoplasms

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