Fig. 4. Light micrographs of 5 µm thick sections illustrating TonEBP immunoreactivity (TonEBP-IR) in the inner medulla of control (A) and 3- (B), 7- (C) and 14- (D) day water-deprived N. alexis. Black arrows indicate the nuclei of the collecting duct epithelial cells that pass through the renal papilla (A–D), and arrowheads indicate the lumen of the collecting ducts. TonEBP-IR was quite strong in the nuclei of the collecting duct epithelial cells in the inner medulla of control mice (A). The intensity of TonEBP-IR in the nuclei increased as the water deprivation period was prolonged (B–D). Scale bar, 30 µm.