FIGURE 3.

NHERF3 inhibits NHE3 activity in response to elevated [Ca₂₊]_i. Na⁺/H⁺ exchange was measured in PS120/NHE3V cells expressing NHERF3 or empty vector control, using the pH-sensitive dye, BCECF, which was loaded into cells during a 15-min incubation with 40 mm NH₄Cl. A, in PS120 cells not expressing NHERF3, elevation of [Ca²⁺]_i by the calcium ionophore, 4-bromo-A23187 (0.5 μm), had no effect on NHE3 activity. B, A23187 treatment in PS120 cells co-expressing NHE3 and NHERF3, resulted in decreased NHE3 activity by ∼40%. Panels A and B represent measurements taken from single experiments. C, bar graph summarizes the mean ± S.E. of 12 experiments similar to that in B. p value (*) is in comparison with control (paired t test).