Non-invasive lung function tests in rats with progressive papain-induced emphysema

Area of Science:

• Pulmonary physiology
• Respiratory system research
• Animal models in medicine

Background:

• Non-invasive plethysmography is crucial for assessing lung function.
• Thoracic gas volume (TGV), airway resistance (Raw), and phase difference (PD) are key respiratory parameters.
• Papain instillation is a common method to induce emphysema-like lung changes in animal models.

Purpose of the Study:

• To adapt non-invasive plethysmographic methods for measuring TGV, Raw, and PD in anesthetized rats.
• To investigate the time course of lung changes induced by papain instillation.
• To evaluate the impact of papain on TGV, Raw, and PD in a rat model.

Main Methods:

• Anesthetized Sprague-Dawley rats were intratracheally instilled with papain (2 or 4 mg/kg) or saline (control).
• Measurements of TGV, Raw, and PD were performed pre-treatment and at 4-day intervals up to 16 days post-treatment.
• Statistical analysis was used to compare parameters between treated and control groups over time.

Main Results:

• TGV increased by 65% by day 4 and plateaued, suggesting papain's destructive effects on lung parenchyma were complete by day 8.
• Airway resistance (Raw) did not differ significantly from control values throughout the study.
• Phase difference (PD) remained unchanged, indicating preserved peripheral airway resistance despite parenchymal destruction.

Conclusions:

• Non-invasive plethysmography is effective for monitoring papain-induced lung injury in rats.
• Papain primarily affects lung parenchyma, leading to increased TGV, while airways remain largely unaffected.
• The observed PD changes are consistent with uneven compliance distribution rather than peripheral resistance inequalities.