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High body temperature induces micronuclei in mouse bone marrow
1Naruto Research Institute, Otsuka Pharmaceutical Factory, Inc., Tokushima, Japan.
Abstract:
The mouse micronucleus test was conducted to investigate the effect of high body temperature on micronucleus induction. Group of 10 male ddY mice were exposed to 30 degrees C for 1, 3 or 6 h, 37 degrees C for 0.5, 1, 2, 3 or 4 h, and 40 degrees C for 1 or 2 h. Bone marrow cells were sampled 24 h after heat exposure. Exposure of mice to 37 degrees C for 3 or 4 h and 40 degrees C for 1 or 2 h raised body temperature to approximately 40.5 degrees C and produced statistically significant increases in micronucleated polychromatic erythrocyte frequencies (8.1 +/- 4.5, 6.0 +/- 2.1, 5.3 +/- 3.3, 7.5 +/- 2.9%, respectively; control frequencies, 2.0 +/- 1.1%). In addition, about 25% of the induced micronuclei were relatively large (diameter of micronucleus > or = 1/4 diameter of cytoplasm). These results suggest that body temperatures of 39.5 degrees C or higher for more than 30 min induce micronuclei in bone marrow cells, and one possible mechanism is disturbance of the mitotic apparatus.
Insights
High body temperatures (39.5°C+) for over 30 minutes significantly increase micronuclei in mouse bone marrow cells. This suggests heat stress can cause genetic damage, potentially by disrupting cell division.
Area of Science:
- Toxicology
- Genetics
- Environmental Health
Background:
- Elevated body temperature (hyperthermia) is a stressor that can impact cellular function.
- The genotoxic effects of hyperthermia are not fully understood.
- The mouse micronucleus test is a standard assay for detecting chromosomal damage.
Purpose of the Study:
- To investigate the relationship between high body temperature and micronucleus induction in mice.
- To determine the threshold temperature and duration for heat-induced genotoxicity.
Main Methods:
- Male ddY mice were exposed to various temperatures (30°C, 37°C, 40°C) for different durations.
- Bone marrow cells were collected 24 hours post-exposure.
- Micronucleated polychromatic erythrocyte frequencies were analyzed.
Main Results:
- Temperatures of 37°C for 3-4 hours and 40°C for 1-2 hours significantly increased micronuclei frequencies.
- These conditions raised mouse body temperature to approximately 40.5°C.
- A notable percentage (25%) of induced micronuclei were relatively large.
Conclusions:
- Body temperatures of 39.5°C or higher for more than 30 minutes induce micronuclei in mouse bone marrow.
- Heat stress may cause genotoxicity through mechanisms like disturbance of the mitotic apparatus.