The crucial role played by calcium as a cellular messenger has become increasingly evident, as has the recognition that cells spend much energy in maintaining the cytosolic concentration of this cation both constant and low. It is thought they do this to avoid precipitating phosphate, needed as a source of bond energy and to modulate protein structure. Moreover, since calcium that does enter the cell must be disposed with, processes that utilize calcium have evolved, e.g. secretion, contraction, signaling, to name just some. New knowledge concerning the processes of cellular calcium entry, extrusion and the fate of intracellular calcium has accumulated in recent years. Much has also been learned about calcium transport by and across epithelial cells. It seems logical to think that the processes of calcium entry, extrusion and intracellular handling are similar in all cells. We have therefore assembled in one volume overviews and research reports of transport and cellular calcium regulation so as to explore similarities and differences between cells that utilize calcium for metabolic purposes and those whose primary function is transport.
