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| TITLE: | The Effect of Altered Nocturnal Melatonin Levels on the Progression of Breast Cancer in Rats | ||
| Principal Investigator |
Gregory Travlos, Ph.D. | Laboratory of Experimental Pathology NIEHS | |
| Health Relevance |
Cancer | ||
| Research Categories |
Toxicology Studies of Whole Animals | Tumor/promotion | Melatonin/Breast Cancer |
| FY95 Funds | DIR-12 $ 2,000 | Start Date 9/93 | End Date 9/96 |
| Rationale and Summary |
There have been reports that exposure to electric and magnetic fields (EMF) lowers nocturnal melatonin levels. Further it has been reported that exposure to magnetic fields will promote chemically-induced breast cancer in the rat. Our rationale is to separate the effect of lowered nocturnal melatonin levels from a possible direct effect of magnetic fields. We have demonstrated that one minute exposures of light will decrease nocturnal melatonin levels in the F344/N rat. Further we have demonstrated that multiple one minute exposures approximately two hours apart will allow a nocturnal rise in melatonin levels but will prevent peak levels. Since the reported effects of magnetic field exposure is a moderate decrease in peak melatonin levels, this model will allow us to test the effect of lowered melatonin levels in a rat breast cancer model. The rationale is that short- term light exposure at night or magnetic field exposure or both will cause a decrease in nocturnal melatonin levels and this may account for the reported association between exposures and increased breast cancer. Since light at night is a proven suppressor of melatonin levels, we will follow this course for investigating the health effects of decreased melatonin levels, thus avoiding the confounding factors that magnetic field exposure may produce. Yet our study will provide important information on with respect to possible adverse health effects associated with magnetic fields. | ||
| Experimental Design and Exposure Conditions |
The model is MNU induced breast cancer in the F344/N rat. The melatonin in the blood and pineal gland is measured using radioimmunoassay after extraction of the melatonin. Positive controls are run in each assay. The animals are coded and the assays run in a blind fashion. The light intensity is measured. The experiments are run under GLP conditions. | ||
| Quality Assurance Measures |
Assay standards, spiked serum samples and curves are run for each melatonin assay. The data will be reviewed by QA personnel. | ||
| Results and Discussion |
The light/dark cycle for the F344/N rat was switched from the standard nighttime to a 3am to 3 pm dark cycle. This allows all nocturnal melatonin assays to be run during standard laboratory hours. We have demonstrated that the nocturnal rise in melatonin can be switched by switching the dark cycle to 3am-3pm. Further we have demonstrated that multiple one minute bursts of light will decrease but not negate the nocturnal melatonin levels. Finally, we have demonstrated that we can reliably and reproducibly measure serum and pineal melatonin levels in the rat. We have constructed a light tight facility in which the light cycle can be switched. | ||
| Recent Publications |
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