A PROFILE ANALYSIS OF PROPAGATING CALCIUM WAVES

The identity of the wave messenger mediating the propagation of intrac ellular Ca2+ waves in a variety of cells is currently controversial. T here is disagreement as to whether the observed waves are mediated by the diffusion of Ca2+ or by the diffusion of inositol 1,4,5-trisphosph ate. Resolution of this question will help to elucidate the mechanisms underlying intracellular Ca2+ waves and oscillations. It has been sug gested that the diffusion coefficient of the wave messenger, D, may be evaluated by means of the profile equation, D = c lambda, where c Is the wave speed, and lambda is the space constant of the wave front. We show that this equation is not, in general, correct. We derive a more comprehensive form of the profile equation, including the effect of b uffering of the wave messenger, and show that the profile equation may be used to estimate the diffusion coefficient of the wave messenger o nly if the details of the reaction and buffering kinetics are known.