INTERCELLULAR SPIRAL WAVES OF CALCIUM

Intercellular calcium waves have been observed in a large number of ce ll types, and are known to result from a variety of stimuli, including mechanical or hormonal stimulation. Recently, spiral intercellular wa ves of calcium have been observed in slices of hippocampal tissue. We use an existing model to study the properties of spiral intercellular calcium waves. Although intercellular spiral waves are well known in t he context of cardiac muscle, due to the small value of the calcium di ffusion coefficient intercellular calcium waves have fundamentally dif ferent properties. We show that homogenisation techniques give a good estimate for the plane wave speed, but do not describe spiral behaviou r well. Using an expression for the effective diffusion coefficient we estimate the intercellular calcium permeability in liver. For the bis table equation, we derive an analytic estimate for the value of the in tercellular permeability at which wave propagation fails. In the calci um wave model, we show numerically that the spiral period is first a d ecreasing, then an increasing, function of the intercellular permeabil ity. We hypothesise that this is because the curvature of the spiral c ore is unimportant at low permeability, the period being approximately set instead by the speed of a plane wave along a line of coupled cell s in one dimension. (C) 1998 Academic Press Limited.