title: CO2 relaxation of the rat lung parenchymal strip.
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 ( [Formula: see text] ) or hypercapnia ( [Formula: see text] ). 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.
authors.affiliation: Pulmonary and Critical Care Medicine (S-111-PULM), VA Puget Sound Health Care System, 1660 South Columbian Way, Seattle, WA 98108, USA. mjemery@u.washington.edu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Emery
authors.forename: Randy L
authors.initials: RL
authors.lastname: Eveland
authors.forename: Jin-Hye
authors.initials: JH
authors.lastname: Min
authors.forename: Jacob
authors.initials: J
authors.lastname: Hildebrandt
authors.forename: Erik R
authors.initials: ER
authors.lastname: Swenson
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000494:pharmacology*; D005260:Female; D016857:Hypocapnia / Q000503:physiopathology; D008168:Lung / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009218:Myosins / Q000187:drug effects / Q000502:physiology; D051381:Rats; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide; D009218:Myosins