Dietary K+ and Cl− independently regulate basolateral conductance in principal and intercalated cells of the collecting duct

The renal collecting duct contains two distinct cell types, principal and intercalated cells, expressing potassium K ir 4.1/5.1 (KCNJ10/16) and chloride ClC-K2 (ClC-Kb in humans) channels on their basolateral membrane, respectively. Both channels are thought to play important roles in controlling systemic water-electrolyte balance and blood pressure. However, little is known about mechanisms regulating activity of K ir 4.1/5.1 and ClC-K2/b. Here, we employed patch clamp analysis at the single channel and whole cell levels in freshly isolated mouse collecting ducts to investigate regulation of K ir 4.1/5.1 and ClC-K2/b by dietary K + and Cl - intake. Treatment of mice with high K + and high Cl - diet (6% K + , 5% Cl - ) for 1 week significantly increased basolateral K + -selective current, single channel K ir 4.1/5.1 activity and induced hyperpolarization of basolateral membrane potential in principal cells when compared to values in mice on a regular diet (0.9% K + , 0.5% Cl - ). In contrast, basolateral Cl - -selective current and single channel ClC-K2/b activity was markedly decreased in intercalated cells under this condition. Substitution of dietary K + to Na + in the presence of high Cl - exerted a similar inhibiting action of ClC-K2/b suggesting that the channel is sensitive to variations in dietary Cl - per se. Cl - -sensitive with-no-lysine kinase (WNK) cascade has been recently proposed to orchestrate electrolyte transport in the distal tubule during variations of dietary K + . However, co-expression of WNK1 or its major downstream effector Ste20-related proline-alanine-rich kinase (SPAK) had no effect on ClC-Kb over-expressed in Chinese hamster ovary (CHO) cells. Treatment of mice with high K + diet without concomitant elevations in dietary Cl - (6% K + , 0.5% Cl - ) elicited a comparable increase in basolateral K + -selective current, single channel K ir 4.1/5.1 activity in principal cells, but had no significant effect on ClC-K2/b activity in intercalated cells. Furthermore, stimulation of aldosterone signaling by Deoxycorticosterone acetate (DOCA) recapitulated the stimulatory actions of high K + intake on K ir 4.1/5.1 channels in principal cells but was ineffective to alter ClC-K2/b activity and basolateral Cl - conductance in intercalated cells. In summary, we report that variations of dietary K + and Cl - independently regulate basolateral potassium and chloride conductance in principal and intercalated cells. We propose that such discrete mechanism might contribute to fine-tuning of urinary excretion of electrolytes depending on dietary intake.