Fluorescence depolarization studies of red cell membrane fluidity. The effect of exposure to 1.0-GHz microwave radiation.

Abstract

The internal viscosity of human red blood cell membranes was investigated during exposure to continuous wave 1.0-GHz microwave radiation using fluorescence measurements of a lipid seeking molecular probe, diphenyl-hexatriene. Samples were exposed in a Crawford cell arranged so that fluorescence was measured during microwave exposure; specific absorption rates calculated from electrical measurements were approximately 0.6, 2 and 15 W/kg. Measurements were obtained at selected temperatures between 15 degrees C and 40 degrees C and as a function of the duration of exposure at 23 degrees C. Arrhenius-type plots of the temperature profile data were linear and showed no difference between exposed and control samples. The exposure duration data also showed no difference between exposed and control samples except for a small effect of elevated temperature at the highest exposure. The activation energy for motion of the fluorescent probe in its environment within the membrane lipid was not affected by the application of the microwave energy and no evidence for a lipid phase transition was found. These results indicate that the increased cation efflux from red cells, observed by others at certain transition temperatures during microwave exposure, was more likely to have been caused by alteration of the membrane bound protein than by changes in the lipid constituents of the red cell membrane.

AI evidence extraction

Main findings

Across 15–40°C, Arrhenius-type temperature profile plots were linear and showed no difference between microwave-exposed and control samples. Exposure-duration measurements at 23°C also showed no difference between exposed and control samples, except for a small effect of elevated temperature at the highest exposure. Activation energy for probe motion was not affected and no evidence for a lipid phase transition was found.

Outcomes measured

• Red cell membrane internal viscosity/fluidity (fluorescence depolarization using diphenyl-hexatriene)
• Activation energy for probe motion in membrane lipid
• Evidence of lipid phase transition (temperature-dependent behavior)

Limitations

• Sample size not reported in abstract
• Exposure duration not specified in abstract
• SAR values are given as approximate and derived from electrical measurements
• In vitro red blood cell membrane measurements may not generalize to in vivo effects

{
    "study_type": "in_vitro",
    "exposure": {
        "band": "microwave",
        "source": null,
        "frequency_mhz": 1000,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Human red blood cell membrane samples (in vitro)",
    "sample_size": null,
    "outcomes": [
        "Red cell membrane internal viscosity/fluidity (fluorescence depolarization using diphenyl-hexatriene)",
        "Activation energy for probe motion in membrane lipid",
        "Evidence of lipid phase transition (temperature-dependent behavior)"
    ],
    "main_findings": "Across 15–40°C, Arrhenius-type temperature profile plots were linear and showed no difference between microwave-exposed and control samples. Exposure-duration measurements at 23°C also showed no difference between exposed and control samples, except for a small effect of elevated temperature at the highest exposure. Activation energy for probe motion was not affected and no evidence for a lipid phase transition was found.",
    "effect_direction": "no_effect",
    "limitations": [
        "Sample size not reported in abstract",
        "Exposure duration not specified in abstract",
        "SAR values are given as approximate and derived from electrical measurements",
        "In vitro red blood cell membrane measurements may not generalize to in vivo effects"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "red blood cells",
        "membrane fluidity",
        "fluorescence depolarization",
        "diphenyl-hexatriene",
        "microwave radiation",
        "1.0 GHz",
        "specific absorption rate",
        "Crawford cell",
        "Arrhenius plot",
        "lipid phase transition"
    ],
    "suggested_hubs": []
}

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