Reduced store-operated Ca2+ currents in rat basophilic leukaemia cells cultured under serum-free conditions

Influx of Ca2+ represents an important regulatory signal in the process of cell proliferation. However, little is known about how Ca2+ entry changes during the cell-cycle. Patch-clamp experiments and microfluorimetry show that store-operated Ca2+ entry was substantially reduced in rat basophilic leukaemia cells cultured for 24 h under serum-free conditions. Likewise, retinoic acid treatment blocked Ca2+ influx activated by store depletion via inositol 1,4,5-trisphosphate. Both procedures are known to arrest cells at the G(0)/G(1) boundary of the cell-cycle and induced a reduction in 5-bromo 2'-deoxyuridine incorporation into DNA. Ca2+ release from the stores remained unaltered and two types of Kf currents were not affected in cells after serum starvation. The specific reduction in Ca2+ entry was not detected when using aphidicolin, 5-fluorouracil or thymidine to synchronise the cell-cycle. These data suggest that store-operated Ca2+ influx changed during cell-cycle progression which might have important implications for cell growth. (C) 2001 Harcourt Publishers Ltd.