Decrease of airway smooth muscle contractility induced by simulated breathing maneuvers is not simply proportional to strain

作者：Pascoe Chris D; Seow Chun Y; Pare Peter D; Bosse Ynuk^*

来源：Journal of Applied Physiology, 2013, 114(3): 335-343.

DOI：10.1152/japplphysiol.00870.2012

• asthma
• airway hyperresponsiveness
• lung maneuvers
• tone
• spasmogen
• stress
• strain

Pascoe CD, Seow CY, Pare PD, Bosse Y. Decrease of airway smooth muscle contractility induced by simulated breathing maneuvers is not simply proportional to strain. J Appl Physiol 114: 335-343, 2013. First published November 29, 2012; doi:10.1152/japplphysiol.00870.2012.-The lung is a dynamic organ and the oscillating stress applied to the airway wall during breathing maneuvers can decrease airway smooth muscle (ASM) contractility. However, it is unclear whether it is the stress or the attendant strain that is responsible for the decline of ASM force associated with breathing maneuvers, and whether tone can prevent the decline of force by attenuating the strain. To investigate these questions, ovine tracheal strips were subjected to oscillating stress that simulates breathing maneuvers, and the resulting strain and decline of force were measured in the absence or presence of different levels of tone elicited by acetylcholine. In relaxed ASM, high stress simulating 20 cm H2O-transpulmonary pressure excursions strained ASM strips by 20.7% and decreased force by 17.1%. When stress oscillations were initiated during measurement of ACh concentration-response curves, tone almost abrogated strain at an ACh concentration of 10(-6) M (1.1%) but the decline of force was not affected (18.9%). When stress oscillations were initiated after ACh-induced contraction had reached its maximal force, strain was almost abrogated at an ACh concentration of 10(-6) M (0.9%) and the decline of force was attenuated (10.1%). However, even at the highest ACh concentration (10(-4) M), substantial decline of force (6.1%) was still observed despite very small strain (0.7%). As expected, the results indicate that tone attenuated the strain experienced by ASM during breathing maneuver simulations. More surprisingly, the reduction of strain induced by tone was not proportional to its effect on the decline of force induced by simulated breathing maneuvers.

• 出版日期2013-2