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Disruption of sodium and water balance in K + ‐adapted BKβ4 −/− mice
Author(s) -
Grimm P Richard,
Holtzclaw J David,
Irsik Debra L,
Liu Liping,
Sansom Steven C
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.606.35
Subject(s) - chemistry , sodium , potassium , bk channel , endocrinology , medicine , calcium , excretion , biochemistry , organic chemistry
Flow‐induced potassium secretion is a physiological response by which the kidneys increase K + secretion from the connecting tubule (CNT). Large, calcium‐activated potassium channels (BK), which are responsible for this response, are expressed in principal and intercalated cells (PCs and ICs) of the CNT. BK in the ICs are a complex of α and β4 subunits (BKα/β4), but their physiological function is uncertain. The goal of this study was to determine whether β4 knockout mice (BKβ4 −/− ) have altered renal salt clearance when fed a K + ‐rich diet (5% K + ) for 10 days. Under control diet conditions (0.6% K + ) no differences were detected between WT and BKβ4 −/− . When BKβ4 −/− consumed the K + ‐rich diet they became volume expanded (Hct − 45.7 ± 0.4% WT vs 35.4 ± 0.4% BKβ4 −/− ; weight change − 0.42 ± 0.03g WT vs 5.2 ± 0.2g BKβ4 −/− ). BKβ4 −/− had lower urine output (180 ± 7μl/hour vs 206 ± 6μl/hour), U Na V (188 ± 7μmol/day vs 433 ± 13μmol/day), and FE Na (0.29 ± 0.03% vs 0.66 ± 0.02%) compared to WT despite having similar food and water consumption. The inability of BKβ4 −/− to minimize Na + absorption led to volume retention, suggesting BKα/β4 of ICs play a role in minimizing Na + absorption. It is unlikely that the ICs of the CNT are directly responsible for the increased Na + absorption due to their low Na + /K + ‐ATPase expression; but during elevated filtrate delivery, ICs may release paracrine factors that influence Na + absorption in neighboring PCs.