Wheel-Running Exercise for 60 Days Does Not Alter Either the Rate of Clearance of Magnetite from Hamster Lungs or Macrophage Organelle Motility

Exercise can enhance the clearance of particles from ciliated airways but its influence on clearance from the lung parenchyma is unclear. We used magnetometry to determine the effect of exercise on the rate of magnetite disappearance from the lungs over 63 days. We also analysed decay of the initial remanent magnetic field (relaxation) to assess macrophage motility. Six control hamsters (93 ± 4 g) were housed in normal animal cages while six others (96 ± 2 g) were exercise-trained by allowing them continuous access to activity wheels. After 4 weeks, each animal was anaesthetized and given a single intratracheal dose of magnetite (0.2 mg in 0.15 ml saline). Following instillation, the exercised hamsters continued voluntary exercise during the remainder of the study. Beginning at 15 min and at various times up to 63 days post-instillation, each animal was magnetized and its remanent magnetic field measured over the lungs with a fluxgate magnetometer. The remanent field immediately following magnetization (Br₀) is proportional to the amount of magnetite remaining in the lung. Br₀ declined exponentially over the 63 day period, but the rate of decline was not affected by exercise. Magnetometry and analysis of intracellular magnetic particle motion can be used as a noninvasive technique for the assessment of both particle retention and macrophage motility. Voluntary exercise for up to 63 days in hamsters did not affect total lung clearance or macrophage organelle motility.