Fig. 2.
Extra-matrix free [Ca2+]. Panels a-e show how extra-matrix free [Ca2+] ([Ca2+]e) changed over time with addition of different amounts of NaCl (0–20 mM) at each [CaCl2] (0–40 μM). Note in Panels b-e that after a rapid rise in [Ca2+]e and its decline as extra-matrix Ca2+ entered the matrix via the CU, added extra-matrix NaCl caused an increase in [Ca2+]e via activation of the NCE. Additionally, Panel e indicates time intervals (arrows) used to derive the rate of change in [Ca2+]e (= slope between 380 and 480 s) via the NCE and the final [Ca2+]e at the end of each experiment (single arrow). The time course of Ca2+ uptake is summarized in Panel f, which illustrates [Ca2+]e as a function of [CaCl2] at three specified time points (see inset, data are obtained from Panels a-e). Note in Panel f that best fitting trendlines are placed through all [Ca2+]e of the same time points (60, 120, 300 s). Data in Panels a-e were obtained from a mitochondrial protein concentration of 0.5 mg/ml and are presented as mean of 4 individual experiments ± SEM