Generalized blocking in S phase by methotrexate.
An attempt was made to enhance the frequency of prometaphase cells for high-resolution-banding studies in untransformed Syrian hamster fibroblasts using a typical methotrexate (MTX) block/bromodeoxyuridine release schedule. The recovery 'wave' was serially sampled and detailed sub-phase analysis made using the replication bands resulting from bromodeoxyuridine uptake. Of the 3 batches of MTX used, one (Sigma greater than 2 years old) was found to have decayed to a non-toxic compound which produced almost no measurable perturbation of the cell cycle at any concentration used. The other 2 (new Sigma and new Lederle), whilst producing mitotic index fluctuations which could be construed to indicate blocking and "synchrony", gave absolutely no evidence of any specific blocking site, but rather a general stoppage (or slowing down) during MTX treatment and continuation in exactly the same order as untreated controls upon release.
Savage
J R
JR
Medical Research Council, Radiobiology Unit, Didcot, Oxon, Great Britain.
Prasad
R
R
D000818:Animals; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D006224:Cricetinae; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D007399:Interphase / Q000187:drug effects*; D008647:Mesocricetus; D008727:Methotrexate / Q000494:pharmacology* / Q000633:toxicity; D008940:Mitotic Index
D001973:Bromodeoxyuridine; D008727:Methotrexate