Fig 1.
Expression of AQP-2 in the cortex and medulla of mouse developing and adult kidneys.
(a) At E14.5, AQP-2 is not expressed in the upmost branched ureteric bud (UB) in the superficial cortex including the terminal tips (T) in nephrogenic zone, but uninterruptedly expressed in the main trunk of UB near the renal hilum (inset). (b-c) At E16.5 and E18.5, AQP-2 starts to discretely express in relatively mature connecting tubules (CNT) that have larger lumen and locates near the small artery (A) and vein (V), and UB trunks (insets). P for the mature proximal tubule. (d-f) After birth, AQP-2 discretely express in the branched cortical collecting duct (CCD) and CNT but not express in distal convoluted tubule (DCT). Inset are the UB or CD in deep medulla. Scales bars = 20 μm and 10 μm (insets).
Fig 2.
Expression of AQP-1 in the cortex of developing kidneys.
(a) At E15.5, in the nephrogenic zone, the ureteric bud tip (T) and newly formed nephrons, Comma (C) -and S (S) -shaped bodies do not express AQP-1 except for those erythrocytes in the first cleft. Beneath the zone, AQP-1 is expressed at endothelium of small arteries (A) and at immature proximal tubules (imP) where the epithelial cells are arranged in a single layer and densely packed; (b) At E18.5, AQP-1 is still expressed at endothelium of small artery (A), and at mature proximal tubules (P) where the single layer of cells are pale stained and not densely packed; (c and d) At P1 and P5, AQP-1 continue to express at the immature (imP) and mature (P) proximal tubule, and at endothelium of arterioles (arrow heads) in cortex, but does not continue expressing at endothelium of artery (A); During development, veins (V) do not express AQP-1 at all. G for glomerulus. Scales bar = 20 μm.
Fig 3.
Expression of AQP-1 in developing and adult renal medulla, showing the countercurrent arrangement of TAL-DVR and DTL-AVR, as well as AQP-1 differentiated expression.
(a) At the medullary level of E14.5 kidney, AQP-1 positive DVR (arrowhead) is located in close contact with AQP-1 negative TAL (asterisk). Thick walled proximal tubule (P) expressing AQP-1 at the brush border are surrounded by AQP-1 negative capillaries (red arrows). The UB trunk and branches do not express AQP-1 at all and stay separated from the tubule-vessel by a vein (V). (b-c) at E15.5 and E18.5, medullary mesenchymal cells (M) in interstitial space are arranged into a ladder-like framework, perpendicular to the pairs of the accompanied tubule-vessel. The AQP-1 positive proximal tubules (P) and descending thin limb (DTL) are surrounded by AQP-1 negative AVR or capillaries (red arrows). TAL (asterisks) are identified by its thick walled epithelium without AQP-1 expression and in proximity to DVR (arrowheads) expressing AQP-1. (d-f) After birth, more and more tubules and vessels extend into medulla and fill up the interstitial space. DVR (arrowheads) are still arranged parallel and close to TAL (asterisk), even in adult kidney (f), while AQP-1 positive proximal tubule (P) and its extension DTL are accompanied by elongated AVR or capillaries (arrowheads) containing AQP-1 positive erythrocytes. Scales bar = 20 μm.
Fig 4.
Double-labeled immunofluorescence for expression of NKCC2 in TAL and AQP1 in DVR or DTL, respectively, showing the countercurrent arrangement of TAL-DVR/DTL in developing and adult medulla.
(a-d) NKCC2 (red) is expressed in the apical plasma membrane of thick walled TAL. AQP1 (green) is expressed in either DVR or DTL. From fetus to newborn (P1), TAL and DVR are always in close contact with each other in the medulla. In adult kidney medulla (P28), more tubules show up, and TAL run parallel to either DVR or DTL (arrow) both with AQP-1 positive expression. Scales bar = 10 μm (a) and 50 μm (b-d).
Fig 5.
The countercurrent arrangement of the TAL and DVR is visualized in 3D representations and corresponding histological images.
(a-d). The courses of TAL (green) and DVR (red) are 3D represented based on digital tracing of serial paraffin or epoxy sections, which correspond to the tubules and vessels pointed by green and red arrows respectively in a1-d1. Blue lines represent the course of the proximal tubules and thin limbs. The grey balls and the grey fan or arc for the glomeruli and nephrogenic zone (a and b) or renal capsule (c and d), respectively, and the white arc for the renal papilla. (a1-d1) The histological images were derived from serial paraffin sections with HE stain (a1 and c1) and serial epoxy sections with toluidine blue stain (b1 and d1). TAL and DVR in a1-d1 are identified by digital tracing, in which DVR tracing started at the efferent arterioles, TAL started from macular densa of same glomerulus as that of the efferent arterioles. Scales bar = 25 μm.