Exercise stress and enzyme-induced emphysema.

Rats were exposed to an aerosol of 10% papain for 8 h found in pilot studies to produce marked emphysema. One week after exposure some animals were forced to exercise in a motor-driven activity wheel 2 h daily for 4 wk, while others remained at rest. Another group of rats which served as the control were exposed to saline under the same conditions and divided into exercise and rest groups. Elastic recoil pressure (Pst) of lung was measured from static deflation pressure-volume curves with air and saline. Pst measured in air-filled lungs was not significantly different between the emphysema-rest and emphysema-exercise groups. When inflated with saline the Pst was significantly reduced in the emphysema-exercise compared to the emphysema-rest group at high and mid (100, 80, 60%) lung volumes. Pst in air- and saline-filled lungs was not significantly different between the control-rest and control-exercise groups. We therefore conclude that mechanical stress resulting from physical exercise decreased Pst of lung tissue in emphysematous rats.