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Inhibitory effects of low doses of melatonin on induction of preneoplastic liver lesions in a medium-term liver bioassay in F344 rats: relation to the influence of electromagnetic near field exposure.

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Imaida K, Hagiwara A, Yoshino H, Tamano S, Sano M, Futakuchi M, Ogawa K, Asamoto M, Shirai T · 2000

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Melatonin supplementation protected against liver cancer development, highlighting why EMF's melatonin-suppressing effects matter for long-term health.

Plain English Summary

Summary written for general audiences

Researchers gave rats different doses of melatonin (a hormone that regulates sleep) and found it decreased early liver cancer lesions. This study was designed to understand why previous EMF exposure experiments in the same bioassay showed a tendency toward fewer preneoplastic liver foci. The authors suggest that an increase in serum melatonin levels is a possible reason for that tendency in the EMF experiments.

Why This Matters

This research provides context for interpreting the earlier EMF exposure experiments in the same bioassay. In this rat study, melatonin treatment decreased preneoplastic liver foci. What makes this particularly relevant is that the authors compared these results with their earlier EMF exposure experiments and suggest that increased melatonin serum levels are a possible reason for the tendency toward decreased preneoplastic liver foci there. Both the numbers and areas of GST-P-positive foci in the liver were decreased in the melatonin treated groups, significant for numbers at 10 ppm. The link to the earlier EMF experiments is the authors' suggestion, not a demonstrated mechanism.

Exposure Information

Specific exposure levels were not quantified in this study. Duration: 6 weeks

Study Details

The effects of different doses of melatonin (1, 5, 10 and 20 ppm in the drinking water) were analyzed in the same bioassay system employed for our previously reported EMF exposure studies.

Six-week-old male F344 rats were given a single dose of diethylnitrosamine (DEN, 200 mg/kg b.w., i.p...

only the first being elevated, while LH and testosterone were reduced. Although clear dose dependenc...

Comparison of the current results with the previously reported findings for EMF exposure experiments, suggests that increase in melatonin serum levels is a possible reason for the associated tendency for decreased preneoplastic hepatocyte foci development.

Cite This Study
Imaida K, Hagiwara A, Yoshino H, Tamano S, Sano M, Futakuchi M, Ogawa K, Asamoto M, Shirai T (2000). Inhibitory effects of low doses of melatonin on induction of preneoplastic liver lesions in a medium-term liver bioassay in F344 rats: relation to the influence of electromagnetic near field exposure. Cancer Lett 155(1):105-114, 2000.
Show BibTeX
@article{k_2000_inhibitory_effects_of_low_2224,
  author = {Imaida K and Hagiwara A and Yoshino H and Tamano S and Sano M and Futakuchi M and Ogawa K and Asamoto M and Shirai T},
  title = {Inhibitory effects of low doses of melatonin on induction of preneoplastic liver lesions in a medium-term liver bioassay in F344 rats: relation to the influence of electromagnetic near field exposure.},
  year = {2000},
  
  url = {https://pubmed.ncbi.nlm.nih.gov/10814886/},
}
PubMed: 10814886

Cited By (34 papers)

Quick Questions About This Study

Yes. In rats given melatonin in drinking water, both the numbers and areas of GST-P-positive preneoplastic foci in the liver were decreased. The decrease was significant for numbers in the 10 ppm group, and clear dose dependence was not apparent.
The authors compared the melatonin results with their earlier EMF exposure experiments in the same bioassay. They suggest that an increase in melatonin serum levels is a possible reason for the tendency toward decreased preneoplastic liver foci in those experiments.
Melatonin treatment (1, 5, 10 and 20 ppm in drinking water) decreased both the numbers and areas of GST-P-positive preneoplastic liver foci in rats, significant for numbers at 10 ppm. The study did not establish how the decrease occurs.
Male F344 rats received a single dose of diethylnitrosamine, then 0, 1, 5, 10 or 20 ppm melatonin in their drinking water for 6 weeks, starting 2 weeks later. Melatonin was given only at night (18:00 to 09:00) to maintain their circadian rhythm.
The study used the same bioassay system as the authors' earlier EMF exposure studies. Rats given diethylnitrosamine had a two-thirds partial hepatectomy at week 3 and were sacrificed at week 8, when serum levels of melatonin, ACTH, corticosterone, LH, FSH and testosterone were measured.