FIGURE 2.

Pretreatment with unlabeled ouabain inhibits donor quenching and acceptor emission. A, comparison of the donor decay in the presence of 10 μm Bodipy-Fl Ouabain (black line) with the donor decay from an experiment in which the oocyte was first pretreated with 10 μm unlabeled ouabain, prior to the addition of 10 μm Bodipy-Fl Ouabain. When the oocyte was pretreated, the donor (gray line) was unquenched as indicated by the slow time constant (2.42 ± 0.02 ms). B, sensitized emission (black line) in the presence of 10 μm Bodipy-Fl Ouabain (same trace as in Fig. 1B). When oocytes were pretreated with cold ouabain, the sensitized emission is absent (the gray line is the background emission; see supplemental Fig. S1B). The decays displayed are from two representative oocytes, one pretreated and one without pretreatment (gray and black lines, respectively).