Differential response of the permeability of the rat liver canalicular membrane to sucrose and mannitol following in vivo acute single and multiple exposures to microwave radiation (2.45 GHz) and radiant-energy thermal stress.

Abstract

Both acute and chronic exposures to microwave radiation altered the function of the rat canalicular membrane. A single acute exposure to microwave radiation [80 mW/cm2, 2.45 GHz, continuous wave, 30 min exposure (SAR approximately equal to 72 W/kg)] or a matched radiant-energy thermal load, both designed to raise core body temperature approximately 3 degrees C, decreased the permeability of the canalicular membrane of male Sprague-Dawley rats to sucrose. The change in canalicular membrane permeability was demonstrated by a significant increase in the percentage of [3H]sucrose recovered in bile following its administration by a segmented retrograde intrabiliary injection. Similar acute exposures to microwave and radiant-energy thermal sources produced no significant alterations in canalicular membrane permeability to [14C]mannitol. In both acute exposure protocols, a rapidly reversible increase in bile flow rate was observed. Four exposures (30 min/day x 4 days) to either microwave radiation (80 mW/cm2) or a matched radiant-energy thermal load resulted in a significant depression in bile flow rate at normothermic temperatures. Animals receiving multiple exposures to microwave radiation had significant decreases in canalicular membrane permeability to both [3H]sucrose and [14C]mannitol, while similar exposure to radiant-energy thermal load alone altered canalicular membrane permeability to [3H]sucrose. An examination of the hepatic clearance of sucrose and mannitol following acute microwave exposure demonstrated no significant differences. Thus acute single exposure to microwave and radiant-energy thermal loads produced similar alterations in canalicular membrane permeability. Conversely, multiple exposures produced nonreversible changes in bile flow rate and canalicular membrane permeability, with microwave exposure producing greater alterations in the function of the canalicular membrane than an equivalent radiant-energy thermal load.

AI evidence extraction

Main findings

A single 30-min microwave exposure (80 mW/cm2, 2.45 GHz, continuous wave; SAR ~72 W/kg) or a matched radiant-energy thermal load (both raising core temperature ~3°C) decreased canalicular membrane permeability to sucrose but not to mannitol, and produced a rapidly reversible increase in bile flow rate. After four daily 30-min exposures, both microwave and matched thermal load depressed bile flow rate at normothermic temperatures; microwave exposure decreased permeability to both sucrose and mannitol, while thermal load altered permeability to sucrose only. Hepatic clearance of sucrose and mannitol after acute microwave exposure showed no significant differences.

Outcomes measured

• Rat liver canalicular membrane permeability to sucrose
• Rat liver canalicular membrane permeability to mannitol
• Bile flow rate
• Hepatic clearance of sucrose and mannitol

Limitations

• Sample size not reported in abstract
• Exposure conditions are high-intensity and include substantial heating (core temperature increase ~3°C), limiting relevance to non-thermal exposures
• Animal study; generalizability to humans is uncertain
• Mechanistic interpretation and blinding/randomization details not provided in abstract

Suggested hubs

• who-icnirp (0.2)
  High-SAR microwave exposure with thermal loading may be relevant to guideline discussions, though no policy content is provided.

{
    "study_type": "animal",
    "exposure": {
        "band": "microwave",
        "source": null,
        "frequency_mhz": 2450,
        "sar_wkg": 72,
        "duration": "Single acute exposure: 30 min; Multiple exposures: 30 min/day x 4 days"
    },
    "population": "Male Sprague-Dawley rats",
    "sample_size": null,
    "outcomes": [
        "Rat liver canalicular membrane permeability to sucrose",
        "Rat liver canalicular membrane permeability to mannitol",
        "Bile flow rate",
        "Hepatic clearance of sucrose and mannitol"
    ],
    "main_findings": "A single 30-min microwave exposure (80 mW/cm2, 2.45 GHz, continuous wave; SAR ~72 W/kg) or a matched radiant-energy thermal load (both raising core temperature ~3°C) decreased canalicular membrane permeability to sucrose but not to mannitol, and produced a rapidly reversible increase in bile flow rate. After four daily 30-min exposures, both microwave and matched thermal load depressed bile flow rate at normothermic temperatures; microwave exposure decreased permeability to both sucrose and mannitol, while thermal load altered permeability to sucrose only. Hepatic clearance of sucrose and mannitol after acute microwave exposure showed no significant differences.",
    "effect_direction": "mixed",
    "limitations": [
        "Sample size not reported in abstract",
        "Exposure conditions are high-intensity and include substantial heating (core temperature increase ~3°C), limiting relevance to non-thermal exposures",
        "Animal study; generalizability to humans is uncertain",
        "Mechanistic interpretation and blinding/randomization details not provided in abstract"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "microwave radiation",
        "2.45 GHz",
        "SAR",
        "rat",
        "liver",
        "canalicular membrane",
        "permeability",
        "sucrose",
        "mannitol",
        "bile flow",
        "thermal stress"
    ],
    "suggested_hubs": [
        {
            "slug": "who-icnirp",
            "weight": 0.200000000000000011102230246251565404236316680908203125,
            "reason": "High-SAR microwave exposure with thermal loading may be relevant to guideline discussions, though no policy content is provided."
        }
    ]
}

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