ClC‐K2 Cl‐ Channel exhibits discrete actions on acid‐base transport of A‐ and B‐Type Intercalated Cells of the Collecting Duct

• Published in: The FASEB journal 2022-05, Vol.36 (S1), p.n/a
• Main Authors: Pyrshev, Kyrylo, Stavniichuk, Anna, Tomilin, Viktor N., Zaika, Oleg, Pochynyuk, Oleh
• Format: Article
• Language: English
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.2022.36.S1.R3619

The collecting duct is a highly adaptive terminal part of the nephron, which is essential for maintaining systemic homeostasis. Principal and intercalated cells perform different physiological tasks and exhibit distinctive morphology. However, acid‐secreting A‐ and base secreting B‐type of intercalated cells cannot be easily separated in functional studies despite virtually mirror opposite localization of their transport acid‐base systems. Here, we used BCECF‐sensitive intracellular pH (pHi) measurements in split‐opened collecting ducts followed by immunofluorescent microscopy in WT and intercalated cell‐specific ClC‐K2‐/‐ mice to demonstrate that ClC‐K2 inhibition enables to distinguish signals from A‐ and B‐ types of intercalated cells. We show that ClC‐K2 Cl‐ channel is expressed on the basolateral side of intercalated cells, where it governs Cl‐‐dependent H+/HCO3‐ transport. ClC‐K2 blocker, NPPB, caused acidification or alkalization in different subpopulations of intercalated cells in WT but not ClC‐K2 ‐/‐ mice. Immunofluorescent assessment of the same collecting ducts revealed that NPPB increased pHi in AE1‐positive A‐type and decreased pHi in pendrin‐positive B‐type of intercalated cells. Induction of metabolic acidosis led to a significantly augmented abundance and H+ secretion in A‐type and decreased proton transport in B‐type of intercalated cells, whereas metabolic alkalosis caused the opposite changes in intercalated cell function, but did not substantially change their relative abundance. Concluding, we show that inhibition of ClC‐K2 can be employed to discriminate between A‐ and B‐type of intercalated cells in split‐opened collecting duct preparations. We further demonstrate that this method can be used to independently monitor changes in the functional status and abundance of A‐ and B‐types in response to systemic acid/base stimuli.