Effects of exercise on particle deposition in Syrian golden hamsters

The effects of exercise and its associated increase in ventilation on the deposition of inhaled particles were investigated. Both total retention and patterns of distribution of a 99mTc sulfur colloid aerosol (activity median aerodynamic diameter, 0.38 micron; geometric standard deviation, 1.35) were measured in male Syrian golden hamsters. Animals were either anesthetized, resting, or exercising on a treadmill during a 15-min aerosol exposure. Each hamster's oxygen consumption (VO2) was continuously monitored during the exposure; immediately after, the animal was killed. The lungs were excised, inflated, and dried in a microwave oven. The rigid lungs were sliced and dissected in a predetermined way so that retention at specific locations could be compared. The radioactivity and weight of 40 pieces from each of 12 hamsters were measured. The uniformity of deposition was described by an evenness index (EI) for each piece: EI = (cpm/g)piece/(cpm/g) whole lung. With theoretical uniformity of retention, all EI values should be 1.0. During aerosol exposure, the exercising group had a VO2 of 5.0 +/- 0.6 (SD) ml STPD/min/100 g, which was 2 times the resting group (2.5 +/- 0.4) and 4 times the anesthetized group (1.2 +/- 0.2). The total retention of particles in the lungs increased in a parabolic manner as a function of VO2; the exercising animals had a retention 6 times greater than the anesthetized animals. The increased retention in running hamsters may reflect either increased ventilation alone or increased collection efficiency. Each animal's activity level also affected local distribution of particles in the lung.(ABSTRACT TRUNCATED AT 250 WORDS)