highly significantp < 0.005
If the cell pH in the experimental period is compared with the average of the control and recovery periods, the difference, 0.04 t 0.01 pH unit, is highly significant (p < 0.005). 592 THE JOURNAL OF GENERAL PHYSIOLOGY " VOLUME 89 - 1987 The cell pH response both in the absence of luminal Na (OpH = 0.04 0.01) and in the absence of capillary Na (OpH = 0.07 0.02) is significantly lower than that seen in the presence of Na on both sides of the cells (p < 0.05 for both comparisons).