Intercalated cell BKα subunit is required for flow-induced K+ secretion
Rolando Carrisoza-Gaytan, Evan C. Ray, Daniel Flores, Allison L. Marciszyn, Peng Wu, Leah Liu, Arohan R. Subramanya, WenHui Wang, Shaohu Sheng, Lubika J. Nkashama, Jingxin Chen, Edwin K. Jackson, Stephanie M. Mutchler, Szilvia Heja, Donald E. Kohan, Lisa M. Satlin, Thomas R. Kleyman
Rolando Carrisoza-Gaytan, Evan C. Ray, Daniel Flores, Allison L. Marciszyn, Peng Wu, Leah Liu, Arohan R. Subramanya, WenHui Wang, Shaohu Sheng, Lubika J. Nkashama, Jingxin Chen, Edwin K. Jackson, Stephanie M. Mutchler, Szilvia Heja, Donald E. Kohan, Lisa M. Satlin, Thomas R. Kleyman
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Research Article Cell biology Nephrology

Intercalated cell BKα subunit is required for flow-induced K+ secretion

Abstract

BK channels are expressed in intercalated cells (ICs) and principal cells (PCs) in the cortical collecting duct (CCD) of the mammalian kidney and have been proposed to be responsible for flow-induced K+ secretion (FIKS) and K+ adaptation. To examine the IC-specific role of BK channels, we generated a mouse with targeted disruption of the pore-forming BK α subunit (BKα) in ICs (IC-BKα–KO). Whole cell charybdotoxin–sensitive (ChTX-sensitive) K+ currents were readily detected in control ICs but largely absent in ICs of IC-BKα–KO mice. When placed on a high K+ (HK) diet for 13 days, blood [K+] was significantly greater in IC-BKα–KO mice versus controls in males only, although urinary K+ excretion rates following isotonic volume expansion were similar in males and females. FIKS was present in microperfused CCDs isolated from controls but was absent in IC-BKα–KO CCDs of both sexes. Also, flow-stimulated epithelial Na+ channel–mediated (ENaC–mediated) Na+ absorption was greater in CCDs from female IC-BKα–KO mice than in CCDs from males. Our results confirm a critical role of IC BK channels in FIKS. Sex contributes to the capacity for adaptation to a HK diet in IC-BKα–KO mice.

Authors

Rolando Carrisoza-Gaytan, Evan C. Ray, Daniel Flores, Allison L. Marciszyn, Peng Wu, Leah Liu, Arohan R. Subramanya, WenHui Wang, Shaohu Sheng, Lubika J. Nkashama, Jingxin Chen, Edwin K. Jackson, Stephanie M. Mutchler, Szilvia Heja, Donald E. Kohan, Lisa M. Satlin, Thomas R. Kleyman

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Figure 4

Perforated whole cell patch recordings of charybdotoxin-sensitive (ChTx-sensitive) currents in intercalated cells (ICs) and principal cells (PCs) in CCDs from IC-BKα–KO and floxed control mice.

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Perforated whole cell patch recordings of charybdotoxin-sensitive (ChTx-...
Recordings were performed in cells clamped at +60 mV. The composition of the bath and pipette solutions, which both contained 130 mM K-gluconate, is given in Methods. Currents were normalized to a membrane capacitance of 13 pF per cell. (A–D) Representative current tracings are shown on the left for ICs in CCDs isolated from floxed control K+–fed (CK-fed) (A), floxed high K+–fed (HK-fed) (B), KO CK-fed (C), and KO HK–fed mice (D). (E) Summary graph showing individual data points and mean ± SD (box with SD bars) for ChTx-sensitive current density in ICs in floxed mice fed a CK diet (n = 4 ICs), averaging 500 ± 65 pA/cell, enhanced to 742 ± 33 pA/cell (n = 4 ICs, P < 0.03) in mice fed a HK diet for 10 days to maximize BK channel expression. BK channel activity in ICs in IC-BKα–KO CCDs isolated from mice fed a HK diet (n = 10 ICs) was minimal. *P < 0.05 compared with CK-fed controls and #P < 0.05 compared with HK-fed controls, 2-tailed unpaired Student’s t test. (F) Summary graph as described for E showing ChTx-sensitive currents in PCs in CCDs from HK-fed IC-BKα–KO mice (n = 6 PCs); these currents were greater than those in HK-fed floxed littermates (n = 5 PCs). *P < 0.05 compared to HK-fed controls, 2-tailed unpaired Student’s t test. Data were obtained from both male and female mice.