Fish cell line (ULF-23HU) derived from the fin of the central mudminnow (Umbra limi): Suitable characteristics for clastogenicity assay

A cell line (ULF-23HU) from the fin of the central mudminnow (Umbra limi) was characterized and tested for its suitability to assess cytogenetic damages induced by chemicals in fish. Cells of this line exhibit a fibroblastlike appearance and grew optimal at 25°C in, TC-199 medium containing 10% fetal bovine serum, but slower growth continued down to 4°C, where they could be stored for prolonged periods. Seeding efficiency of ULF-23HU cells on the plastic substratum was approximately 85% in the above culture medium at 25°C. They had a 32-h cell cycle time taken up by a 20-h S period as determined by the autoradiographic analysis of the fraction of labeled mitosis. Cultures showed relatively high mitotic index (0.84 to 2.35%) during exponential growth phase lasting about 7 d. Karyological analysis of the cells at the different subculture passages revealed constant chromosome modal number of 23 consisting of metacentric or submetacentric chromosomes, which were primarily similar to those of in vivo cells, with one additional chromosome. The spontaneous sister chromatid exchange rate was 5.3 per metaphse. When ULF-23HU cells were exposed to N-nitroso-N-methylurea, a clastogen in the mammalian cells, dose-dependent increases both in sister chromatid exchanges and chromosome aberrations were clearly detected. These results on the growth kinetics and cytogenetic characteristics offered the high possibility of the use of this cell line as a suitable in vitro model for clastogenicity studies in fish.