Figure 5. Flow-dependent stimulation of the forward mode of NCX activity.

A, cells expressing Δ(241–680) were pre-treated with ATP + Tg in Na-PSS + 0.3 mm EGTA; gramicidin was not used in these experiments. Ba²⁺ uptake was initiated by applying 1 mm Ba²⁺ in K-PSS. The labelled points designate the superfusion of 5 ml of 0.3 mm EGTA in K-PSS (a) or Na-PSS (b, c). Error bars are shown for every fourth data point (n = 5). B, experimental conditions as in A. The labelled points designate the superfusion of 5 ml of 0.3 mm EGTA in K-PSS (a) or Na-PSS (c), or, for b, the removal of 0.3 mm EGTA in K-PSS and its rapid replacement with 1 ml of 0.3 mm EGTA in Na-PSS (n = 4). C, experimental conditions as in A. The labelled points designate the repeated superfusions of 5 ml of 0.3 mm EGTA in K-PSS (n = 4). D, slopes of the traces over the time intervals designated by the lines beneath the traces labelled 1–5 in panels A–C. *P < 0.05 versus slope at time interval 1. †P < 0.05 for data at time interval 2 for superfusion (A) versus rapid replacement (B).