Molecular Machineries of Signaling in Kidney Macula Densa.

肾黄斑致密区（MD）腔内NaCl浓度（[NaCl]）的变化通过影响一氧化氮（NO）的释放来调节肾小管肾小球反馈（TGF）反应。在新建立的小鼠黄斑致密细胞系（NE-MD）中，我们证明了Na^+- k ^+- 2cl ^-共转运蛋白抑制剂速尿和低[Cl^-]同样诱导nNOS蛋白表达和l -精氨酸诱导的NO生成的增加。我们还发现NE-MD细胞中检测到的nNOS样蛋白（60kD）比通常从脑和骨骼肌中获得的nNOS样蛋白（160kD）要小。利用双向电泳和质谱（MALDI-TOF-MS）分析了NE-MD nNOS蛋白的分子结构。根据肽段的质谱分析，我们得出结论，在速尿诱导的NE-MD nNOS蛋白中，nNOS还原域的主要部分被删除。

Changes in the luminal NaCl concentration ([NaCl]) at the kidney macula densa (MD) modulate the tubuloglomerular feedback (TGF) responses via affecting the release of nitric oxide (NO). In a newly established mouse macula densa cell line (NE-MD), we demonstrated that furosemide, an inhibitor of Na^+-K^+-2Cl^- cotransporter, and low [Cl^-] similarly induced increases in both the nNOS protein expression and the L-Arg-induced NO generation. We also found that the nNOS-like protein (60kD) determined in the NE-MD cells was smaller in size than the usual nNOS proteins (160kD) obtained from brain and skeletal muscle. Molecular structure of the NE-MD nNOS protein was carefully analyzed by the two-dimensional electrophoresis and the mass spectrometry (MALDI-TOF-MS). Based on the observation of the MS analysis of the peptide piece, we conclude that a main part of the nNOS reduction domain has been deleted in the furosemide-induced nNOS protein of NE-MD.