The effect of dietary glycine on the hepatic tumor promoting activity of polychlorinated biphenyls (PCBs) in rats

Rodica Petruta Bunaciu, Job C. Tharappel, Hans Joachim Lehmler, Izabela Kania-Korwel, Larry W. Robertson, Cidambi Srinivasan, Brett T. Spear, Howard P. Glauert

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Polychlorinated biphenyls (PCBs) are ubiquitious lipophilic environmental pollutants. Some of the PCB congeners and mixtures of congeners have tumor promoting activity in rat liver. The mechanism of their activity is not fully understood and is likely to be multifactorial. The aim of this study was to investigate if the resident liver macrophages, Kupffer cells, are important in the promoting activity of PCBs. The hypothesis of this study was that the inhibition of Kupffer cell activity would inhibit hepatic tumor promotion by PCBs in rats. To test our hypothesis, we studied the effects of Kupffer cell inhibition by dietary glycine (an inhibitor of Kupffer cell secretory activity) in a rat two-stage hepatocarcinogenesis model using 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB-153, a non-dioxin-like PCB) or 3,3′,4,4′-tetrachlorobiphenyl (PCB-77, a dioxin-like PCB) as promoters. Diethylnitrosamine (DEN, 150 mg/kg) was administered to female Sprague-Dawley rats, which were then placed on an unrefined diet containing 5% glycine (or casein as nitrogen control) starting two weeks after DEN administration. On the third day after starting the diets, rats received PCB-77 (300 μmol/kg), PCB-153 (300 μmol/kg), or corn oil by i.p. injection. The rats received a total of 4 PCB injections, administered every 14 days. The rats were euthanized on the 10th day after the last PCB injection, and the formation of altered hepatic foci expressing placental glutathione S-transferase (PGST) and the rate of DNA synthesis in these foci and in the normal liver tissue were determined. Glycine did not significantly affect foci number or volume. PCB-153 did not significantly increase the focal volume, but increased the number of foci per liver, but only in the rats not fed glycine; PCB-77 increased both the foci number and their volume in both glycine-fed and control rats. Glycine did not alter the PCB content of the liver, but did increase the activity of 7-benzyloxyresorufin O-dealkylase (BROD) in liver microsomes from PCB-153 treated rats. However, glycine did not affect the induction of ethoxyresorufin O-dealkylase activity by PCB-77 in liver microsomes. Glycine diminished hepatocyte proliferation in PGST-positive foci, but not in normal tissue. Overall these results do not support the hypothesis that dietary glycine inhibits the promoting activities of PCBs. The observations that PCB-153 increased the number of foci per liver in control rats but not glycine-fed rats and that dietary glycine reduced cell proliferation in PGST-positive foci, however, do not allow us to completely rule out a role for dietary glycine. But the data overall indicate that Kupffer cells likely do not contribute to the tumor promoting activities of PCB-77 and PCB-153.

Original languageEnglish
Pages (from-to)147-155
Number of pages9
Issue number3
StatePublished - Oct 8 2007

Bibliographical note

Funding Information:
We are grateful to Dr. Chantal A. Rivera (Baylor College of Medicine, TX) and Dr. Ion Deaciuc (University of Louisville, KY) for useful information regarding the glycine model. This research was supported by NIEHS (ES07380, ES012475, ES013661) and the Kentucky Agricultural Experiment Station. R.P. Bunaciu was supported by the Training Core of the Superfund Basic Research Program (ES07380).


  • 2,2′,4,4′,5,5′-Hexachlorobiphenyl
  • 3,3′,4,4′-Tetrachlorobiphenyl
  • Glycine
  • Hepatocyte proliferation
  • Kupffer cells
  • Tumor promotion

ASJC Scopus subject areas

  • Toxicology


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