Mathematical modelling of Ca2+ oscillations in airway smooth muscle cells

The action of different agonists such as acetylcholine on the membrane of airway smooth muscle cells may induce cytosolic Ca2+ oscillations which can be a part of the Ca2+ signalling pathway, eventually leading to cell contraction. The aim of the present study is to present a mathematical model of the possible effect of the initial Ca2+ distribution within the cell on the form and frequency of induced Ca2+ oscillations. It takes into account intracellular Ca2+ stores such as sarcoplasmic reticulum and cytosolic proteins as well as Ca2+ exchange across the plasma membrane. We are able to demonstrate a closer agreement of model predictions with observed Ca2+ traces for a significantly wider range of parameter values, as was previously reported. We show also that the total cellular Ca2+ content is an important system parameter especially because of the content in sarcoplasmic reticulum. At a total Ca2+ increase of about 20%, the oscillation frequency increases by 25%; also, damped oscillations become sustained. Cases are indicated in which such a situation could occur.