Figure 6. Acute exposure to 10 nm T₃ increases intracellular Ca²⁺ content and release.

A, control [Ca²⁺]_i transients elicited by field stimulation at 1 Hz. Exposure to T₃ for 5 min increased baseline [Ca²⁺]_i and [Ca²⁺]_i transient amplitude without affecting relaxation of [Ca²⁺]_i transients. After 10 min of exposure to T₃ there were further increases in both baseline [Ca²⁺]_i and [Ca²⁺]_i transient amplitude. Washout of T₃ restored control parameters. B, control recordings from another atrial cell show [Ca²⁺]_i transients followed by SR Ca²⁺ release induced by rapid exposure to10 mm caffeine. Acute exposure to 10 nm T₃ increased baseline [Ca²⁺]_i, [Ca²⁺]_i transient amplitude and SR Ca²⁺ release induced by 10 mm caffeine.