Figure 7.
Monensin effects on the pHt. Application of 20 µM monensin to Na-based cytosolic solutions causes little change in the HPTS signal. After exposure to monensin, the HPTS fluorescence signals in three Na-based cytosolic solutions of different pH, where the t-system is depolarized, were used to calibrate the pH in the t-system. The decrease in pHt at the end of the trace after the exchange of the Na-based solution with the K-based polarizing solution of the same pH causes a decrease in the HPTS signal, indicating that monensin was incorporated into the t-system membrane as described in the text. Solution exchanges are indicated by the vertical pale bars, and the composition of the internal solution is indicated by the horizontal lines above the trace.