Fig. 7.

Pervanadate-induced protein phosphotyrosine levels decrease after acute treatment with the electrogenic potassium ionophore valinomycin. A, Valinomycin-treated (+) HEK 293 cells were preincubated in serum-free medium containing valinomycin (5 μg/ml + 0.1% ethanol) for 10 min and then treated with pervanadate (250 μm; 30 min) in the continued presence of valinomycin. Control cells [without valinomycin (−)] were preincubated and pervanadate-treated with serum-free medium containing 0.1% ethanol vehicle. After pervanadate treatment (+), cell lysates were prepared, and lysate proteins were separated by SDS-PAGE, transferred to nitrocellulose, and probed with anti-phosphotyrosine antibody. B, Protein phosphotyrosine signals were quantified in each lane by densitometry, and values are expressed relative to the pervanadate without valinomycin condition (n = 6; ***p ≤ 0.005, Student’s t test).