Method for determining the lung burden of talc in rats and mice after inhalation exposure to talc aerosols.

A 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 micrograms Mg per g lung in rats and less than 0.1 microgram 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 micrograms Mg per g rat lung (n = 17) and 6.5 +/- 2.9 micrograms 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 micrograms 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 micrograms talc per g lung (n = 10) for exposures at 2.3, 4.3, and 17 mg talc m-3, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)