Static mechanical properties of lungs from adrenalectomized pneumonectomized rats

Area of Science:

• Physiology
• Pulmonary Medicine
• Endocrinology

Background:

• Partial pneumonectomy (PNX) triggers compensatory lung growth.
• Adrenalectomy (ADX) is known to affect growth and metabolism.

Purpose of the Study:

• To investigate the impact of adrenalectomy on lung pressure-volume characteristics and compensatory growth following pneumonectomy in rats.

Main Methods:

• Adult male Sprague-Dawley rats underwent unoperated (UNOP), left pneumonectomy (PNX), adrenalectomy (ADX) alone, or ADX followed by PNX (ADX/PNX).
• Pressure-volume curves of saline-filled lungs were analyzed at 2 and 4 weeks post-PNX, measuring maximum lung volumes (MLV) and lung volumes at zero transpulmonary pressure (Ptp).
• Lung collagen and elastin concentrations were assessed, and the effects of hydrocortisone acetate administration were evaluated in ADX/PNX rats.

Main Results:

• Two weeks post-PNX, MLV was reduced by 20% in PNX and 37% in ADX/PNX rats compared to UNOP controls, despite increased right lung mass.
• At 4 weeks, MLV approached normal but remained lower, with ADX/PNX showing MLV 35% below predicted for lung mass.
• Adrenalectomy reduced relative tissue compliance, an effect blocked by hydrocortisone acetate, while PNX alone did not alter compliance.

Conclusions:

• Maximum lung volume (MLV) recovery does not parallel lung mass increase during compensatory lung growth after pneumonectomy.
• Adrenalectomy exacerbates the discrepancy between lung mass and MLV, suggesting hormonal regulation of lung volume.
• Adrenalectomy impairs lung tissue compliance, indicating a role for adrenal hormones in maintaining lung mechanical properties.