RESUMO
Objective: To investigate the effect of extracellular potassium (K+) concentration on the activities of sodium chloride co-transporter (NCC) and large conductance Ca2+-activated K+ channel (BK) in distal renal tubule of mice. Methods: Six specific pathogen free (SPF) C57BL/6 mice aged 8 to 10 weeks were sacrificed,and the kidney slices were made with previously reported method. Then,these slices were incubated randomly in normal K+,high K+,BaCl2 and RbCl solutions,respectively. The abundance and phosphorylation level of NCC in kidney slices at different K+ concentrations and different time courses were detected by Western blotting. The overall and membrane expressions of BK in kidney slices were also detected after incubation with different K+ solutions for 2 h. Results: Compared with normal K+ solution,NCC phosphorylation level was significantly decreased after incubation with high K+ solution for 5,15,30 min (all P<0.05),and NCC phosphorylation level was also decreased after intervention with K+ channel inhibitor Ba2+ or Rb+ (both P<0.05). After the treatment with high K+ solution for 2 h,neither the overall cell expression of BKα subunit and β4 subunit,nor membrane expression of BKα subunit was found significant changes compared with normal K+ incubation. Conclusion: High K+ can directly down-regulate NCC phosphorylation level,which may be preparation for kaliuresis of the downstream tubule of distal convoluted tubule.