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Antagonistic effect of magnesium chloride on the nickel chloride-induced inhibition of DNA replication in Chinese hamster ovary cells. | LitMetric

AI Article Synopsis

  • Nickel chloride (NiCl2) inhibits semiconservative DNA replication in a time- and concentration-dependent manner, with a maximal reduction in DNA synthesis observed within the first hour at 2.5 mM, the highest noncytotoxic concentration.
  • After exposure to NiCl2, the inhibition of DNA synthesis was found to be reversible; however, a sustained 50-60% reduction in DNA synthesis persisted for at least 36 hours after treatment with 2.5 mM NiCl2.
  • The inhibition of DNA replication caused by NiCl2 can be prevented by adding magnesium chloride (MgCl2), although this does not significantly affect the uptake of nickel ions by cells.

Article Abstract

The degree of inhibition of semiconservative DNA replication induced by nickel chloride (NiCl2) was analyzed by radiolabeled-thymidine incorporation alone or with cesium chloride (CsCl) density gradient centrifugation. The onset and duration of this Ni2+-induced inhibition was time- and concentration-dependent, but the degree of inhibition was not. A maximal reduction in the rate of DNA synthesis was observed within the first hour of treatment with 2.5 mM NiCl2, which was the highest noncytotoxic concentration utilized. After six hours, 500 microM and 1 mM as well as 2.5 mM NiCl2 all produced the same 50% to 60% reduction in [3H]-thymidine incorporation into DNA. The inhibitory effect of nickel ions on DNA synthesis was reversible. The rate of DNA synthesis following a 500 microM or 1 mM NiCl2 treatment began to increase after washout of nickel, but a six-hour exposure of cells to 2.5 mM NiCl2 produced a sustained 50% to 60% suppression of DNA synthetic activity for at least 36 hours. At all concentrations of NiCl2 used in this study, some inhibition of DNA synthesis persisted for at least 48 hours, but by 72 hours after treatment, the rate of [3H]-thymidine incorporation was actually 10% above the control. Examination of autoradiographic slides of cells treated with 2.5 mM NiCl2 for six hours demonstrated a 60% reduction of silver grains, but there was no preferential reduction in the quantity of grains in the nucleolus or any other region. Cesium chloride density gradient analysis of the replication of nucleolar DNA in cells treated with 2.5 mM nickel supported the autoradiographic findings. The inhibitory effect of NiCl2 on DNA replication was prevented by the addition of magnesium chloride (MgCl2) to cells maintained in a simple salts/glucose medium (SGM). This effect did not appear to be due to an antagonism of the cellular uptake of nickel by Mg2+, since the maximally effective dose of Mg2+ reduced 63Ni2+ uptake by no more than 25% while the inhibition of replication was completely reversed.

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Source
http://dx.doi.org/10.1002/jbt.2570010203DOI Listing

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