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Nitroprusside upregulates renal betaine/GABA transporter by membrane insertion
Author(s) -
Kempson Stephen A,
Anderson Bailey M,
Levi Moshe,
Blaine Judith
Publication year - 2011
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.25.1_supplement.1038.11
Subject(s) - chemistry , tonicity , sodium nitroprusside , nitric oxide , biophysics , osmolyte , intracellular , symporter , biochemistry , endocrinology , microbiology and biotechnology , transporter , biology , organic chemistry , gene
Nitric oxide (NO) production in the renal medulla plays an important role in sodium and water homeostasis, and NO synthase isoforms are expressed in medullary nephron segments. We previously demonstrated increased NO production by mouse medullary nephron segments in response to NaCl hyperosmolarity (Nitric Oxide 17:33–43, 2007). However a role for NO during osmotic stress in unclear. MDCK cells pre‐loaded with DAF‐FM were used to confirm that the NO donor nitroprusside (NP) produced an increase in intracellular NO. In contrast, intracellular calcium was unchanged (Fura‐2). When MDCK cells were switched from isotonic to hypertonic medium (500 mOsm) containing 1 mM NP the uptake of 3H‐GABA was increased by 96% (p<0.001) within 3 hr compared to hypertonic controls. This suggests that NO may accelerate the hypertonic upregulation of the renal betaine/GABA transporter, BGT1. However, activation by NP was not reproduced by membrane –permeable analogs of cyclic GMP. To understand the mechanism we used MDCK cells transfected with EGFP‐tagged BGT1 and used TIRF microscopy combined with FRAP. Initial data (n=2) show that the rate of recovery of plasma membrane fluorescence after photobleaching was increased more than 2‐fold in the presence of 1 mM MP compared to hypertonic controls. NP may accelerate insertion of BGT protein into the basal plasma membrane during hypertonic stress.