RELATIONSHIP BETWEEN [CA2+] CHANGES IN NUCLEUS AND CYTOSOL

The free calcium concentration in nucleus ([Ca2(+)]n) and in cytoplasm ([Ca2(+)]c) of single cells were estimated by confocal laser microscopy using the Ca2+-indicator Indo-1. It is shown that in various cell types a nucleo-cytosolic Ca2+-gradient is present at rest and during stimulation. The direction and the extent of the nucleo-cytosolic Ca2+-gradient may vary with the cell type, differentiation status, phosphorylation conditions and also with the type of agonist. Evidence is given for the role of extra- and intranuclear storage sites as well as for Ca2+-influx. Finally potential artefactual interference with the measurements is discussed.