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CO2 relaxation of the rat lung parenchymal strip

Authors
Journal
Respiratory Physiology & Neurobiology
1569-9048
Publisher
Elsevier
Publication Date
Volume
186
Issue
1
Identifiers
DOI: 10.1016/j.resp.2012.12.014
Keywords
  • Alveolar
  • Pulmonary Mechanics
  • Ventilation-To-Perfusion Matching
  • Myosin

Abstract

Abstract Evidence from liquid-filled rat lungs supported the presence of CO2-dependent, active relaxation of parenchyma under normoxia by unknown mechanisms (Emery et al., 2007). This response may improve matching of alveolar ventilation (V˙A) to perfusion (Q˙) by increasing compliance and V˙A in overperfused (high CO2) regions, and decrease V˙A in underperfused regions. Here, we have more directly studied CO2-dependent parenchymal relaxation and tested a hypothesized role for actin–myosin interaction in this effect. Lung parenchymal strips (∼1.5mm×1.5mm×15mm) from 16 rats were alternately exposed to normoxic hypocapnia (PCO2≈20 mmHg) or hypercapnia (PCO2≈53 mmHg). Seven specimens were used to construct length-tension curves, and nine were tested with and without the myosin blocker 2,3-butanedione monoxime (BDM). The results demonstrate substantial, reversible CO2-dependent changes in parenchyma strip recoil (up to 23%) and BDM eliminates this effect, supporting a potentially important role for parenchymal myosin in V˙A/Q˙ matching.

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