Fig. 5.

Extracellular Ca²⁺ modulates amiodarone induced Ca²⁺ burst and toxicity, (a) tuminescence from aequorin-coelenterazine was monitored as described in Fig. 1a upon addition of 40 µM amiodarone (arrow). Luminescence was abolished upon addition of 6.8 mM EGTA and recovered upon reintroduction of 1 mM CaCl₂, showing a requirement for extracellular Ca²⁺. Higher levels of CaCl₂ (10 mM) also blocked luminescence, (b) Viability of cultures treated in (a) was assessed on YPD agar, immediately following luminescence measurements, as described in Fig. 2a. Note the increased viability of cells treated with EGTA alone, and with EGTA plus 10 mM CaCl₂, relative to control (no EGTA) and EGTA plus 1 mM CaCl₂. Data are representative of four independent experiments.