Modelling the electrophysiological endothelial cell response to bradykinin

The goal of the present study is to construct a biophysical model of the coronary artery endothelial cell response to bradykinin. This model takes into account intracellular Ca2+ dynamics, membrane potential, a non-selective cation channel, and two Ca(2+)-dependent K+ channels, as well as intra- and extracellular Ca2+ sources. The model reproduces the experimental data available, and predicts certain quantities which would be hard to obtain experimentally, like the individual K+ channel currents when the membrane potential is allowed to freely evolve, the implication of epoxyeicosatrienoic acids (EETs), and the total K+ released during stimulation. The main results are: (1) the large-conductance K+ channel participates only very little in the overall response; (2) EETs are required in order to explain the experimental current-potential relationships, but are not an essential component of the bradykinin response; and (3) the total K+ released during stimulation gives rise to a concentration in the intercellular space which is of millimolar order. This concentration change is compatible with the hypothesis that K+ contributes to the endothelium-derived hyperpolarizing factor phenomenon.