CLASSES AND MECHANISMS OF CALCIUM WAVES

The best known calcium waves move at about 5-30 mum/s (art 20-degrees- C) and will be called fast waves to distinguish them from slow (contra ctile) ones which move at 0.1-1 mum/s as well as electrically propagat ed, ultrafast ones. Fast waves move deep within cells and seem to unde rlie most calcium signals. Their velocity and hence mechanism has been remarkably conserved among all or almost all eukaryotic cells. In ful ly active (but not overstimulated) cells of all sorts, their mean spee ds lie between about 15-30 mum/s at 20-degrees-C. Their amplitudes usu ally lie between 3-30 muM and their frequencies from one per 10-300 s. They are propagated by a reaction diffusion mechanism governed by the Luther equation in which Ca ions are the only diffusing propagators, and calcium induced calcium release, or CICR, the only reaction; altho ugh this reaction traverses various channels which are generally modul ated by IP3 or cADPR. However, they may be generally initiated by a se cond, lumenal mode of CICR which occurs within the ER. Moreover, they are propagated between cells by a variety of mechanisms. Slow intracel lular waves, on the other hand, may be mechanically propagated via str etch sensitive calcium channels.