Two different approaches for the calculation of the endocytosis time constant.

(A) Deconvolution of the reacidification time course from the alkaline vesicle population dynamics and estimated endocytosis time course. For analysis, experimental data from the action potential number series was used (stimulation paradigms: 200 pulses at 20 Hz). Stimulus begin was at 40 seconds. (B) Calculation of the time course of the surface pool, which is determined by the alkaline vesicle population (fluorescence time course at pH 5.5) subtracted from the total pHluorin (fluorescence time course at pH 7.5). The endocytosis time constants were calculated by monoexponential curve fitting. Stimulus begin was at 40 seconds.