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Basolateral transport of bicarbonate by avian renal proximal tubule cells in culture
Author(s) -
Ghanem Kahina,
Laverty Gary
Publication year - 2013
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.27.1_supplement.937.12
Subject(s) - dids , bicarbonate , chemistry , reabsorption , epithelial polarity , bumetanide , cotransporter , forskolin , ion transporter , biophysics , transporter , acid–base homeostasis , biochemistry , endocrinology , kidney , in vitro , biology , membrane , sodium , organic chemistry , gene
Bicarbonate (HCO 3 − ) is an important component of acid/base regulation. Therefore, it is crucial to understand the mechanism of bicarbonate reabsorption in the kidney proximal tubule (PT). In mammals HCO 3 − reabsorption is well understood, but evidence suggests that birds may use a different mechanism. We hypothesize that in the avian PT HCO 3 − crosses the luminal membrane in ionic form, rather than as CO 2 , and that HCO 3 − ions then leave the basolateral side via an NBC1‐like transporter, as in the mammalian PT. Experiments used primary cell cultures of chick PT and electrophysiological studies to measure currents (I SC ) associated with ion transport. Monolayers were first stimulated with 1μM forskolin, which activated a chloride secretory current in the avian PT. This was followed by basolateral application of 100 μM DIDS, an inhibitor of NBC1. With bicarbonate in the bathing solution DIDS caused an increase in I SC of 6.25 ± 1.55 μAmps/cm 2 (n = 6), but only 2.30 ± 0.58 μAmps/cm 2 (n = 5) in the absence of bicarbonate. The increased I SC is consistent with inhibition of electrogenic transport of HCO 3 − ions via the NBC1 transporter, and the decreased effect of DIDS in the nominal absence of bicarbonate further supports this. Additional studies support both mRNA expression and NBC1 protein expression (western blotting) in chick PT cultures and native tissue. Experiments are underway to test for an alternative apical transporter.