Effects of cadmium and zinc ions on mitotic activity and protein synthesis in mouse liver

Alina Smalinskienė, Rasa Gailevičiūtė, Vaiva Lesauskaitė¹, Ilona Sadauskienė, Oleg Abdrakhmanov, Leonid Ivanov

Institute for Biomedical Research, ¹Institute of Cardiology, Kaunas University of Medicine, Lithuania

Key words: cadmium, zinc, mitotic index, protein synthesis, mouse liver.

Summary. Objective. To evaluate the in vivo effects of cadmium and zinc ions on mitotic activity and protein synthesis in mouse liver.

Material and methods. White outbred mice were injected intraperitoneally with cadmium chloride solution (14 µmoles cadmium per 1 kg of body mass) and/or with zinc sulfate solution (48 µmoles zinc per 1 kg of body mass). Histological slides were examined by light microscopy. For each specimen, the number of mitotic cells was counted in 10 randomly selected reference areas. Protein synthesis was evaluated by incorporation of [¹⁴C]-labeled leucine into newly synthesized peptides and proteins.

Results. We found that the mitotic index of mouse liver cells was increased for periods of 2–8 h after cadmium chloride injection; after 24 h the mitotic index significantly diminished. These data indicate a possible increase in liver cell regeneration during the initial 8 h following acute cadmium exposure. Zinc ions did not affect liver mitotic activity, and, interestingly, decreased the mitotic index in the liver of cadmium-treated mice to control levels. An examination of the kinetics of protein synthesis in mouse liver over a 24 h period after cadmium chloride injection revealed that incorporation diminished by 38% at 2 h, then increased 51% by 8 h and again decreased by 32% at 24 h as compared to control. Zinc ions increased protein synthesis in mouse liver 8 h after zinc sulfate injection. In assessing the effects of cadmium and zinc ions in vivo, it appeared that zinc ions tended to protect protein synthesis in response to cadmium ions but only at 2 h after cadmium intoxication.

Conclusions. Zinc ions are capable of normalizing an increase in the mitotic index of liver cells at the early stage of cadmium poisoning (up to 8 h) and to protect the liver translation machinery against inhibition by cadmium.

Correspondence to A. Smalinskienė, Institute for Biomedical Research, Kaunas University of Medicine, Eivenių 4, 50009 Kaunas, Lithuania. E-mail: alina@kmu.lt

Received 18 April 2005, accepted 6 June 2005