Fig. 2.

Amiodarone induced toxicity and Ca²⁺ influx are both dependent on metabolic state. (a) Yeast cultures were grown to stationary phase and transferred to fresh SC medium for 0.5 h (left panel) or 5 h (right panel). Viability was assessed on YPD agar after 15 min exposure to amiodarone (0–80 µM). Cells (0.5 0D_{600 nm} units) were spotted in serial fivefold dilutions in each column, (b–c) Ca²⁺ influx was monitored in cultures freshly transferred (0.5 h) from stationary phase to SC medium or after 5 h. tuminescence is in arbitrary units (AU). Dose dependence of amiodarone-induced aequorin-coelenterazine luminescence is greatly diminished in stationary phase cells (b), but recovers after 5 h growth in fresh medium (c). The arrow indicates the injection point of amiodarone. Data are representative of at least two experiments, (d) Time-dependent recovery of Ca²⁺ influx (luminescence) following transfer to fresh SC medium. The arrow indicates injection of 40 µM amiodarone. (e) Time-dependence of Ca²⁺ influx (luminescence) of cultures grown as in (d), but in the presence of 50 g mL⁻¹ cycloheximide. Data are representative of at least two separate experiments. (f) Aequorin-coelenterazine luminescence of yeast cultures grown to stationary phase and transferred to fresh media with (SC+Glc) or without (SC−Glc) 2% glucose, or 2% glucose in water (Glc) for 2.5 h before injection of 40 µM amiodarone (arrow).