Figure 2

Dose-response (D-R) relationships and time course of intracellular Ca²⁺ responses generated by ATP, UTP, or UDP in TIC cells. (A) Images show a typical fluorescence increase of theca cells loaded with Fluo4-AM dye upon stimulation with 100 μM ATP at 0, 10, or 40 s. (B) D-R relationship (left panel) for the intracellular Ca²⁺ increase elicited by ATP, expressed as a percent of the basal level of arbitrary units of fluorescence (AUF), and time course of the response elicited by 1 mM ATP (right panel). (C) and (D) show experiments similar to those in (B) but applying UTP or UDP, respectively, instead of ATP. (E) D-R curves of the theca cell response to UTP (left) or UDP (right) in Ca²⁺-free Krebs. The stimulus was applied at the time indicated by an arrow and was maintained to the end of the recording. Data points represent the mean ± S.E.M. from 25 to 40 cells in each of 3 independent experiments.