Lung structure and function with age in normal rats and rats with papain emphysema

Area of Science:

• Pulmonary Medicine
• Experimental Pathology
• Respiratory Physiology

Background:

• Intrapulmonary papain instillation in animals models emphysema.
• The long-term effects and natural history of papain-induced lung lesions are not well understood.

Purpose of the Study:

• To investigate the structural and functional lung changes over time in rats following a single papain exposure.
• To determine if papain-induced lung lesions progress or heal with aging.

Main Methods:

• Rats were exposed to papain aerosol at 2 months of age.
• Lung function (specific airways' conductance, diffusing capacity, functional residual capacity) and morphometric parameters (lung volume, mean chord length, internal surface area) were assessed at 4, 8, and 18 months of age.
• Comparison was made between papain-exposed and control groups.

Main Results:

• Papain exposure led to increased mean chord length and functional residual capacity, and decreased internal surface area, diffusing capacity per unit alveolar volume, and diffusing capacity at 4 and 18 months.
• Lung lesions showed no signs of progression or healing over the 18-month study period.
• Lung growth was similar in both control and papain-exposed groups.

Conclusions:

• A single papain-induced lung injury results in a fixed parenchymal deficit.
• Progressive lung destruction likely necessitates repeated or continuous injury, rather than a single event.