THE FREE CYTOPLASMIC CALCIUM-CONCENTRATION OF TUMORIGENIC AND NON-TUMORIGENIC HUMAN SOMATIC-CELL HYBRIDS

The fluorescent indicator of Ca2+ concentration, quin-2, has been used to measure the concentration of free Ca2+ in the cytoplasm of tumorigenic and non-tumorigenic human somatic cell hybrids. The cell hybrids were derived from the fusion of a HeLa derivative (D98 AH2) and normal human fibroblasts. The Ca concentration of the tumorigenic cell lines was 180 .+-. 7 nM and the level in the non-tumorigenic cells was 136 .+-. 6 nM. This difference was statistically highly significant (P < 0.001). Control experiments are reported which show that the level of 3a2+ measured is not influenced by cell density or by the concentration of quin-2-tetra-(acetoxymethyl)ester used in these experiments. The possible implications of this elevated level of cytoplasmic Ca in tumorigenic cells are discussed.