Changes in Fura-2 and Mag-fluo-4 fluorescence are consistent with the expected changes in PHM1-41 myometrial cell ([Ca2+]i) and ([Ca2+]L), respectively. Cells loaded with the dyes were exposed to (A) OT (100 nM), (B) thapsigargin (TG, 100 nM), or (C) CPA (10 μM) in the absence of extracellular Ca2+. After Ca2+ changes stabilized, cells were exposed to Ca2+-free buffer (0 Ca, blue line) or 1 mM extracellular Ca2+ (green line) in A and B. C) CPA was added as described for thapsigargin and was then removed from one group of cells by washing with calcium-free buffer (wash) at the time indicated. Both the washed (green line) and unwashed (blue line) cells were then exposed to 1 mM extracellular Ca2+. Additions of OT, CPA, wash, and Ca2+ are indicated by arrows. Each line represents an average of the responses of 35–40 cells in one of three similar experiments.