Figure 3.

Effect of quercetin on KCl cotransport (KCC) activity in RBCs from SCA patients. RBCs were pre-incubated for 30 min at 37°C in air without or with quercetin (100 μM) in N-MBS. They were then equilibrated for 20 min in Eschweiler tonometers at the required O₂ tension in the continued absence (control) or presence of quercetin. KCC activities, defined as the differences of clotrimazole-insensitive K⁺ influx in the absence and presence of Cl⁻, were measured. Ouabain (100 μM) and bumetanide (10 μM) were present in all experiments, and influxes were normalized to those of control RBCs at 100 mmHg. (A) RBCs were pre-incubated for 30 min at 37°C in air without or with quercetin (100 μM) in N-MBS, equilibrated in Eschweiler tonometers and KCC activity measured in the continued absence or presence of quercetin. Histograms represent means ± SEM, n = 3, *p < 0.05, comparing RBCs in the absence and presence of quercetin. (B) RBCs were first pre-incubated in N-MBS without or with NEM (1 mM) for 45 min at 37°C, 20% Hct. Both aliquots were divided and subsequently incubated without or with quercetin for 30 min, after which aliquots were diluted 10-fold into flux tubes and KCC activity measured as described in (A). All incubations were carried out in air. Histograms represent means ± SEM, n = 5. **p < 0.01, comparing RBCs in the groups indicated.