Figure 9.

H₂O₂ inhibits basolateral K⁺ efflux and NKCC1 activity. A) T₈₄ monolayers were preloaded with the K⁺ tracer ⁸⁶Rb⁺ and treated with H₂O₂ (500 μM) bilaterally for 30 min prior to basolateral treatment with CCh. The efflux of ⁸⁶Rb⁺ into the basolateral bathing solution was measured by scintillation counting. Data were expressed as mean ± SE peak rate of ⁸⁶Rb⁺ efflux. B) T₈₄ monolayers were treated with H₂O₂ for 30 min prior to basolateral incubation in CCh for 1 min and transfer to a basolateral ⁸⁶Rb⁺-containing buffer for 3 min (n=8). The bumetanide insensitive and sensitive components of the response were assessed by incubating inserts in bumetanide (10 μM) concurrently with CCh treatment (n=5). C) T₈₄ monolayers were depleted of intracellular Cl⁻ for 60 min prior to treatment as in B, but with H₂O₂ and CCh solutions prepared in Cl⁻-free buffer. Cells were then transferred to basolateral ⁸⁶Rb⁺ buffer containing Cl⁻ (n=9). Data are presented as mean ± SE rate of K⁺ uptake (μmol K⁺/g protein/min). *P<0.05; ***P<0.001 vs. control (untreated cells). ^#P<0.05; ^##P<0.01; ^###P<0.001 vs. cells treated with CCh alone.