Figure 8.

PDBu increases the Na sensitivity of Na,K-ATPase in permeabilized COS-7 cells. After preincubation in the absence (C, open bars) or presence of 10⁻⁷ M PDBu (P, filled bars) at 37°C, COS-7 cells were permeabilized by freeze–thawing. The hydrolytic activity of Na,K-ATPase was measured in permeabilized cells in the presence of increasing Na concentrations (from 0 to 70 mM). Results are expressed as a fraction of the maximal Na,K-ATPase activity and are means ± SE from 12 independent experiments (* p < 0.05). The maximal Na,K-ATPase activity was 484 ± 26 and 348 ± 34 pmol of ATP × μg of protein⁻¹ × h⁻¹ ± SE for control and PDBu-treated cells, respectively.