Inhalation of a radioactively labeled monodisperse aerosol in rats for the assessment of regional deposition and clearance.

Unanesthesized male Sprague-Dawley rats, averaging 261 g of weight (s.d. = 9 g), were exposed to a radioactively (198Au) labeled monodisperse carnauba wax aerosol, whose AMMD was 0.54 micrometers with a sigma g of 1.1, to determined the alveolar deposition and clearance of particles. Results indicate that 74% of the initial lung burden is cleared in phase one with a T/2 of 11 hours. The remaining 26%, conventionally considered to be the alveolar deposit, is cleared with a T22 of 320 hours. Excised lungs from serial sacrifices have also been measured. The retention curve resulting form the pooled lung data per each day compared well with the curve of the whole animals counted in vivo.