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  • Title: Ultrastructural characterization of murine limb buds after in vitro exposure to grepafloxacin and other fluoroquinolones.
    Author: Shakibaei M, Baumann-Wilschke I, Rücker M, Stahlmann R.
    Journal: Arch Toxicol; 2002 Jan; 75(11-12):725-33. PubMed ID: 11876506.
    Abstract:
    The effects of selected quinolones (levofloxacin, lomefloxacin, temafloxacin and grepafloxacin) on growth and differentiation of murine limb buds were studied in vitro. Ciprofloxacin and ofloxacin served as controls. We used limb buds from 12-day-old mouse embryos that were grown for 6 days in a serum-free, standard or magnesium-deficient medium. Besides evaluation under a dissecting microscope, we used electron microscopy to characterize the effects in detail. The following results are noteworthy. (1) Comparing the effects of standard and magnesium-deficient medium after 3 and 6 days in culture, we found ultrastructural changes after 6 days only. (2) Direct comparison of ofloxacin (racemate) and levofloxacin (L-enantiomer) showed that they had a similar, rather low, potential for affecting cartilage development. (3) The effects of temafloxacin and ciprofloxacin were more pronounced in magnesium-deficient medium, but those of the other drugs were not. (4) Grepafloxacin was the most active quinolone in this assay. It impaired growth and differentiation of limb buds at 30 mg/l; at higher concentrations the explants did not grow. With lower concentrations of 10 mg grepafloxacin/l, no effects were detectable under a dissecting microscope but characteristic changes were seen by electron microscopy. We observed electron-dense aggregates on and within chondrocytes, detachment of the cell membrane from the matrix with matrix-free pericellular areas around chondrocytes, and swelling of cell organelles such as mitochondria and rough endoplasmic reticulum. (5) The affinity of grepafloxacin for divalent cations (Mg2+, Ca2+) was studied by measuring the fluorescence of grepafloxacin solution at various concentrations of Mg2+ and Ca2+. Grepafloxacin showed a relatively high affinity for Ca2+ in the fluorescence assay, which was more pronounced than the affinities of six other fluoroquinolones tested before.
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