MECHANISMS OF BRONCHIAL HYPERRESPONSIVENE SS - ROLE OF SMOOTH-MUSCLE

The understanding of the cellular and molecular mechanisms involved in the contraction of airway smooth muscle has tremendously advanced in the recent years. Extracellular messengers that control the muscle con traction as well as both the membrane transduction processes and the a ctivation of the contractile proteins are known in some details. Sensi tization alters the contractility of airway smooth muscle. It increase s shortening in the early phase of the contraction when rapidly cyclin g cross bridges are operative. At the molecular level, the responsible mechanism is an increment in the activity of the processes leading to phosphorylation of the myosin light chain. Such an alteration in the airway smooth muscle contractility may be observed in the early phase of the development of bronchial hyperresponsiveness.