Relaxation of tracheal smooth muscle is impaired in innate airway hyperresponsiveness

Abstract

The current study was designed to determine whether the nonspecific in vivo airway hyperresponsiveness of the inbred Fisher F-344 rat strain is associated with impaired spontaneous relaxation of airway smooth muscle.Strips of the posterior portion of the trachea from 10 adult Fisher and 10 adult Lewis rats were electrically stimulated at pH 7.4, 2.5 mM Ca 2+ concentration, at 37uC. Both isotonic and isometric relaxations of tracheal smooth muscle (TSM) were investigated. Half time for isotonic relaxation at preload was markedly prolonged in Fisher rats (8.33¡3.21 s) compared with Lewis rats (3.53¡0.54 s; p,0.001). Maximum lengthening velocity at preload and peak rate of isometric tension decline were significantly decreased in Fisher rats compared with Lewis rats. The ratio of shortening velocity to lengthening velocity at preload, as well as the ratio of the isometric peak rates of tension development to tension decline were higher in Fisher rat TSM than in Lewis rat TSM. These differences were associated with a six-fold higher expression of myosin light chain kinase in Fisher rats than in Lewis rats.In Fisher rats, these results suggest that innate airway hyperresponsiveness is associated with both a reduced level and a slower rate of TSM spontaneous relaxation, promoting maintenance of airway constriction.

Bronchial asthma and COPD due to irritants in the workplace - an evidence-based approach

“…However the true population-attributable risk due to occupational exposure is unclear [6,557] as occupational COPD is rarely clinically diagnosed. Blanc et al [558] recently published an ecological analysis using data from three large studies, comprising the Burden of Obstructive Lung Disease study [169], the Latin American Project for Investigation of Obstructive Lung Disease (PLATINO) and the European Community Respiratory Health Survey follow-up (ECHRS II), where occupational COPD was also not a primary goal. The original publications are mainly concerned with OA or asthma symptoms, but a history of pre-existing OA or RADS cannot be allowed to exclude occupational COPD [559].…”

“…The original publications are mainly concerned with OA or asthma symptoms, but a history of pre-existing OA or RADS cannot be allowed to exclude occupational COPD [559]. Blanc et al [558] stressed that the contribution of occupational exposure cannot be ignored, because “the association between adverse working conditions and COPD (…) carries significance as a global finding (…), alongside the (…) critical contribution of cigarette smoking to disease prevalence”.…”

Acción de la simvastatina en la contracción de músculo liso de anillo traqueal inducida por estímulo químico y térmico

“…De lo anterior se puede afirmar que la simvastatina y la regulación del colesterol, influyen en los canales de calcio de la membrana de las células musculares lisas de las vías aéreas al ser estimuladas con agua fría. El cálculo de la velocidad de contracción y la relajación del músculo se reporta principalmente en músculo aislado, señalándose la velocidad como el cambio de longitud en segundos [21,22], no encontrándose referencias de velocidades de contracción para el anillo traqueal de manera íntegra. Los músculos usados por los diferentes autores son de animales cuyo volumen celular es mayor al de la rata [23,24].…”

Mechanics and energetics of myosin molecular motors from nonpregnant human myometrium

“…The period of spontaneous contractions was also recorded. Velocities were expressed in Lo/s, tension in mN/mm 2 , first tension derivatives in mN•s Ϫ1 •mm Ϫ2 , length in %Lo, time indexes (TPT, TPS, and con-traction duration; spontaneous period of contraction) in seconds, and CSA in mm 2 .…”

“…The onset of the common pathway is indicated by (1). The end of the common pathway is indicated by (2). The second part of the 3 V-L phase planes presented a common pathway, during which there was a one-to-one relationship between length and velocity, independent of time.…”