AbstractA method has been developed to quantitate talc lung burdens in rats and mice after inhalation exposure to talc aerosols. The method is based on acid‐insoluble magnesium (Mg) determination by flame atomic absorption. Precipitating protein from homogenates of lungs of unexposed rodents with 5 perchloric acid and washing with 5 trichloroacetic acid removed the soluble and naturally occurring Mg. This resulted in residual Mg content averaging 0.43 μg Mg per g lung in rats and less than 0.1 μg Mg per g lung in mice for young rodents less than 12 weeks old. Rodents 12–18 months old had residual mean (±SD) Mg contents of 3.4 ± 2.0 μg Mg per g rat lung (n=17) and 6.5 ± 2.9 μg Mg per g mouse lung (n=12). Thus, the background residual acid‐insoluble Mg content in rodent lungs appears to increase with age. Negligible quantities of Mg were extracted directly from the talc treated by these procedures. Adding 50–2000 μg talc to lungs from unexposed rodents, followed by the sample treatment, gave mean (±SD) Mg recoveries of 89 ± 12 (n=19) for rat lungs and 96 ± 26 (n=15) for mouse lungs. The lung burden of talc in rodents exposed to talc aerosols for 6 h per day, 5 days per week for 4 weeks was determined. Mean lung burdens in rats were 77, 187, and 806 μg talc per g lung (n=10) for exposures at 2.3, 4.3, and 17 mg talc m3, respectively. Mean lung burdens in mice were 114, 325 and 1150 μg talc per g lung (n=10) for exposures at 2.2, 6.3 and 20.6 mg talc m3, respectively. The coefficient of variation for the lung burdens of the different exposure groups
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