Microwave radiation (2450 MHz) alters the endotoxin-induced hypothermic response of rats.

Abstract

The parenteral administration of bacterial endotoxin to rats causes a hypothermia that is maximal after approximately 90 minutes. When endotoxin-injected rats were held in a controlled environment at 22 degree C and 50% relative humidity and exposed for 90 minutes to microwaves (2450 MHz, CW) at 1 mW/cm2, significant increases were observed in body temperature compared with endotoxin-treated, sham-irradiated rats. The magnitude of the response was related to power density (10 mW/cm2 greater than 5 mW/cm2 greater than 1 mW/cm2). Saline-injected rats exposed for 90 minutes at 5 mW/cm2 (specific absorption rate approximately 1.0 mW/g) showed no significant increase in body temperature compared with saline-injected, sham-irradiated rats. The hypothermia induced by endotoxin in rats was also found to be affected by ambient temperature alone. Increases in ambient temperature above 22 degree C in the absence of microwaves caused a concomitant increase in body temperature. This study reveals that subtle microwave heating is detectable in endotoxin-treated rats that have impaired thermoregulatory capability. These results indicate that the interpretation of microwave-induced biological effects observed in animals at comparable rates and levels of energy absorption should include a consideration of the thermogenic potential of microwave.

AI evidence extraction

Main findings

Endotoxin-injected rats exposed for 90 minutes to 2450 MHz continuous-wave microwaves at 1 mW/cm2 had significantly higher body temperature than endotoxin-treated sham-irradiated rats, with a power-density-related magnitude (10 mW/cm2 > 5 mW/cm2 > 1 mW/cm2). Saline-injected rats exposed for 90 minutes at 5 mW/cm2 (SAR approximately 1.0 mW/g) showed no significant body temperature increase versus saline sham controls.

Outcomes measured

• Body temperature
• Endotoxin-induced hypothermic response
• Thermoregulatory response under controlled ambient conditions

Limitations

• Sample size not reported in the abstract.
• Exposure metrics are incomplete (e.g., SAR reported only for one condition; not reported for all power densities).
• Animal model with endotoxin-induced impaired thermoregulation may limit generalizability to other conditions.
• Ambient temperature effects are noted as a confounder/important factor, but detailed control/analysis is not provided in the abstract.

{
    "study_type": "animal",
    "exposure": {
        "band": "microwave",
        "source": null,
        "frequency_mhz": 2450,
        "sar_wkg": 1,
        "duration": "90 minutes"
    },
    "population": "Rats",
    "sample_size": null,
    "outcomes": [
        "Body temperature",
        "Endotoxin-induced hypothermic response",
        "Thermoregulatory response under controlled ambient conditions"
    ],
    "main_findings": "Endotoxin-injected rats exposed for 90 minutes to 2450 MHz continuous-wave microwaves at 1 mW/cm2 had significantly higher body temperature than endotoxin-treated sham-irradiated rats, with a power-density-related magnitude (10 mW/cm2 > 5 mW/cm2 > 1 mW/cm2). Saline-injected rats exposed for 90 minutes at 5 mW/cm2 (SAR approximately 1.0 mW/g) showed no significant body temperature increase versus saline sham controls.",
    "effect_direction": "mixed",
    "limitations": [
        "Sample size not reported in the abstract.",
        "Exposure metrics are incomplete (e.g., SAR reported only for one condition; not reported for all power densities).",
        "Animal model with endotoxin-induced impaired thermoregulation may limit generalizability to other conditions.",
        "Ambient temperature effects are noted as a confounder/important factor, but detailed control/analysis is not provided in the abstract."
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "microwave radiation",
        "2450 MHz",
        "continuous wave",
        "power density",
        "specific absorption rate",
        "rats",
        "endotoxin",
        "hypothermia",
        "thermoregulation",
        "heating"
    ],
    "suggested_hubs": []
}

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