Fig. 4.

T₃ Induces Intracellular Ca²⁺ Mobilization

A, HeLa cells labeled with Fluo-4-AM (•) or cells treated with both BAPTA-AM and Fluo-4-AM (○) were superfused with HEPES-buffered Ringer solution (see Materials and Methods). Five consecutive images with 6-sec intervals were obtained before T₃ treatment. Cells were then treated with 10 nm T₃ for 180 sec, and 45 consecutive images were obtained during and after T₃ treatment for 270 sec. Representative images before (control) and 150 sec after T₃ treatment are presented. Changes in fluorescence intensities are indicated by pseudo-colors. The fluorescence intensities of individual cells were measured and are expressed as a ratio of the averaged intensities obtained from five images before T₃ stimulation. Results are means ± se (n = 38–45). B, HeLa cells labeled with the ratiometric Ca²⁺ indicator Indo-1-AM (•) or cells treated with both BAPTA-AM and Indo-1-AM (○) were treated with T₃ as described above. Indo-1 was excited at 351 nm. Emissions at 400–445 nm (FS) and longer than 445 nm (FL) were captured simultaneously. Indo-1 ratios (a ratio of FS to FL) in individual cells were calculated and expressed relative to the averaged ratio obtained from five images before T₃ stimulation. Results are means ± se (n = 30–35).