Role of Ca2+ in preserving viability of Friend erythroleukaemic cells after ultramicroinjection.

Ca2+ facilitated the fusion by Sendai virus of Friend erythroleukaemic cells and Ehrlich ascites tumour cells but not that of hepatoma tissue culture cells. In the absence of Ca2+ Sendai virus caused the complete depletion of ATP and abolished protein synthesis in Friend erythro-leukaemic cells fused with each other. Addition of high concentrations of Ca2+ (10-20 mM) partially protected the cells from ATP depletion. After a further incubation of cells in complete medium plus 0.2 mM adenine, ATP levels and protein synthesis were restored to 60-85% of those of the untreated control. The protective effect of Ca2+ was used to improve the ultramicroinjection method which involves the fusion of human erythrocyte ghosts with cells. When human erythrocyte ghosts containing high K+ were fused with Friend erythroleukaemic cells in the presence of 10 mM Ca2+ ATP levels and protein synthesis after recovery were about 60-85% of the control. Friend erythroleukaemic cells subjected to ultramicroinjection under these conditions had a cloning efficiency of 75-95% of that of the untreated controls. In these experiments 70-100% of the cells had fused with ghosts. Induction of haemoglobin synthesis by dimethylsulphoxide was unimpaired in cells subjected to ultramicroinjection under the same conditions.