Fig. 2.

Progesterone induces rapid cellular calcium responses in HEK293 cells. a Fura-2-loaded HEK293 cells were resuspended in buffer with 1.5 mM CaCl₂ without EGTA or Ca²⁺-free buffer with 1 mM EGTA. At t = 60 s, 160 μM progesterone (P4) was added to the cells. Representative calcium traces are shown. b Cells were treated with 4 μM U-73122, an inhibitor of PLC or 4 μM U-73343, an inactive analogue of U-73122 (control), at 37°C for 2.5 min. Calcium responses to 100 μM acetylcholine or 160 μM progesterone were analyzed. The data represent means ± SD (n = 3). ***p < 0.001, n.s. not significant (U-73122 vs. U-73343)