Static mechanical properties of lungs from adrenalectomized pneumonectomized rats

R. A. Bennett, J. L. Addison and D. E. Rannels The pressure-volume characteristics of saline-filled lungs of adult rats were studied after left pneumonectomy (PNX), with or without prior bilateral adrenalectomy (ADX). Male Sprague-Dawley rats (200-240 g) remained unoperated (UNOP) or were divided into three surgical groups: left PNX, ADX alone, or PNX preceded 5 days earlier by ADX (ADX/PNX). Two weeks post-PNX, maximum lung volumes [MLV; measured at transpulmonary pressure (Ptp) of 10 cmH2O] of right lungs from PNX and ADX/PNX rats remained 20 and 37% below UNOP values, respectively, although right lung mass was equal to or exceeded that of both lungs in UNOP controls. Four weeks postoperative, MLVs approached but remained below normal values. In the ADX/PNX group, MLV was 35% below that predicted for lung mass. The effects of ADX on both lung mass and MLV were blocked by daily injections of ADX/PNX animals with hydrocortisone acetate (5 mg/kg). Neither PNX nor ADX/PNX altered lung volume at zero Ptp or changed the concentration of lung collagen or elastin. When corrected for differences in MLV, relative tissue compliance was unaffected by PNX but was reduced by ADX/PNX. These results indicate that MLV is not restored in parallel with lung mass during the rapid phase of compensatory tissue growth, which follows partial pneumonectomy, and that this discrepancy is accentuated by adrenalectomy.