Fig. 4. Caffeine-induced Ca²⁺ release in spermatogonia, spermatocytes and spermatids. Effects of 10 mM caffeine on [Ca²⁺]_i release in Fura-2-loaded spermatogonia (A,D), pachytene spermatocytes (B,E), round spermatids (C,F). A single cell was equilibrated in KHH, then caffeine was added as pointed by the arrow. Panels (A,B,C) represent response to caffeine following cell preincubation in plain MEM. Panels (D,E,F) represent caffeine-induced Ca²⁺ release following cell preincubation in MEM additioned with 10 mM CaCl₂. The signal was calibrated with 5 µM ionomycin. [Ca²⁺] values are representative of six different experiments for each cell type.