Unmodified calcium concentrations in tumour necrosis factor receptor subtype-mediated apoptotic cell death.

Tumour necrosis factor-alpha (TNF) receptors mediate a variety of effects dependent on cell type. A role for Ca2+ in TNF-induced death remains uncertain. Here we investigated restricting intracellular/extracellular Ca2+ in HeLa epithelial carcinoma cells expressing low and high levels of p75TNFR receptor subtype and KYM-1 rhabdomyosarcoma cells, models of rapid TNF-induced apoptosis. Ca2+ -chelators EGTA and BAPTA-AM as well as microsomal Ca2+ -ATPase inhibitor thapsigargin, did not alter TNF-induced death. TNF was also unable to alter resting [Ca2+]i levels which remained < 200 nM even during times when these cells were undergoing apoptotic cell death. These findings indicate no role for modulated Ca2+ concentrations in TNF-induced apoptotic cell death.