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Expression and activity of epithelial sodium channel in rat cardiac tissue
Author(s) -
Michea Luis Fernando,
Venegas Fabiola,
Gonzalez Andres,
Gonzalez Magdalena,
Knepper Mark A
Publication year - 2006
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.20.5.lb9
Subject(s) - epithelial sodium channel , myocyte , ouabain , chemistry , ventricle , endocrinology , medicine , western blot , sodium , extracellular , sodium channel , nav1.5 , microbiology and biotechnology , biology , biochemistry , organic chemistry , gene
Intracellular sodium concentration ([Na + ] i ) in heart tissue is tightly linked to inotropic and pathological states. We studied the expression and function of the epithelial sodium channel (ENaC) in rat cardiac myocytes. Using RT‐PCR we detected α, β and γ ENaC subunits mRNAs in rat left ventricle. Similar results were obtained with neonatal rat cultured cardiac myocytes. Western Blot studies with ventricular total protein homogenates using anti α, β and γ ENaC antibodies demonstrated the presence of specific inmunoreactive bands of 96, 102 and 92 kDa, respectively, consistent with the bands seen in epithelial tissue. Inmunoprecipitation assays with anti‐β ENaC co‐precipitated α and γ ENaC; α and β ENaC were co‐precipitated with anti‐γ ENaC. Functional studies were performed using benzamil (specific ENaC blocker, 10 −6 M) in isolated adult rat ventricular myocytes loaded with the fluorescent Na + ‐sensitive dye, SBFI. [Na + ] i was determined by in situ calibration using cation selective ionophores. Benzamil (10 min) significantly diminished [Na + ] i in adult ventricular myocytes from 9.6±0.1 mM to 6.2±1.4 mM ( P <0.05, n=12). [Na + ] i did not change in vehicle controls (11.90 ± 0.02 mM, N.S.). Further inhibition of Na + ‐K + ATPase with ouabain (1mM, 10 min) increased [Na + ] i to 43±4 mM in control cardiomyocytes but only to 26±3 mM in benzamil‐treated cells ( P <0.05). The results are consistent with the expression of functional ENaC channels in rat heart. FONDECYT 1050690.