Excitation-contraction coupling mechanisms in airway smooth muscle: new targets in drug design.

Homeostatic regulation of Ca2+ levels within airway smooth muscle cells, and the consequences of changes in intracellular Ca2+ levels are reviewed, and a number of mechanisms are identified as targets for drug action. In the prophylaxis of asthma--by preventing the induction of contraction--the opportunities relate to receptor antagonism, the inhibition of Ca2+ influx, the inhibition of intracellular Ca2+ release, calmodulin antagonism, and the antagonism of contractile proteins. In the symptomatic relief of asthma--by reversal of established contractile responses--the opportunities relate to the inhibition of Ca2+ influx, the inhibition of inositol trisphosphate metabolism, the inhibition of protein kinase C, and the augmentation of Ca2+ removal mechanisms.