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Hydration status affects osteopontin expression in the rat kidney

View Article: PubMed Central - PubMed

ABSTRACT

Osteopontin (OPN) is a secretory protein that plays an important role in urinary stone formation. Hydration status is associated with the development of urolithiasis. This study was conducted to examine the effects of dehydration and hydration on OPN expression in the rat kidney. Animals were divided into three groups, control, dehydrated, and hydrated. Kidney tissues were processed for light and electron microscope immunocytochemistry, in situ hybridization, and immunoblot analysis. Dehydration induced a significant increase in OPN protein expression, whereas increased fluid intake induced a decrease in protein expression. Under control conditions, OPN protein and mRNA expression were only detected in the descending thin limb (DTL). Dehydration induced increased expression in the DTL and the development of detectable expression in the thick ascending limb (TAL). In contrast, OPN expression levels declined to less than the controls in the DTL after hydration, while no expression of either protein or mRNA was detectable in the TAL. Immunoelectron microscopy demonstrated that hydration status altered tubular ultrastructure and intracellular OPN expression in the Golgi apparatus and secretory cytoplasmic vesicles. These data confirm that changes in oral fluid intake can regulate renal tubular epithelial cell OPN expression.

No MeSH data available.


Related in: MedlinePlus

Light micrographs illustrating OPN immunostaining and in situ hybridization in the kidney from control (A–C), dehydrated (D–F) and hydrated (G–I) rats. The OPN immunostaining and hybridization signal increased remarkably in dehydrated animals, while it decreased in hydrated animals relative to control animals. OPN expression was primarily observed in the tubular profiles in the inner stripe of the outer medulla (ISOM). Note that the OPN immunostaining and hybridization signal were not only observed in the descending thin limb of Henle's loop (DTL), but also in the thick ascending limb (TAL) in dehydrated animals (E and F). Arrows indicate an abrupt transition from the OPN-negative proximal tubule (PT) to the OPN-positive descending thin limb of Henle's loop. Quantitative analysis of OPN protein and mRNA expression (J). OSOM, outer stripe of the outer medulla; IM, inner medulla. *p < 0.05 by two-tailed t-test versus control. Scale bars = 1 mm (G), 20 µm (H and I).
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Figure 2: Light micrographs illustrating OPN immunostaining and in situ hybridization in the kidney from control (A–C), dehydrated (D–F) and hydrated (G–I) rats. The OPN immunostaining and hybridization signal increased remarkably in dehydrated animals, while it decreased in hydrated animals relative to control animals. OPN expression was primarily observed in the tubular profiles in the inner stripe of the outer medulla (ISOM). Note that the OPN immunostaining and hybridization signal were not only observed in the descending thin limb of Henle's loop (DTL), but also in the thick ascending limb (TAL) in dehydrated animals (E and F). Arrows indicate an abrupt transition from the OPN-negative proximal tubule (PT) to the OPN-positive descending thin limb of Henle's loop. Quantitative analysis of OPN protein and mRNA expression (J). OSOM, outer stripe of the outer medulla; IM, inner medulla. *p < 0.05 by two-tailed t-test versus control. Scale bars = 1 mm (G), 20 µm (H and I).

Mentions: In control animals, OPN immunoreactivity was observed in the descending thin limb of Henle's loop in the inner stripe of the outer medulla (panel A in Fig. 2). Immunostaining was strongest in the initial part of the descending thin limb, continuous with the S3 segment of the proximal tubule (panel B in Fig. 2). Occasionally, faint immunostaining was observed in some proximal tubules and the parietal epithelium of Bowman's capsule (data not shown). Overall, the level of immunolabeling in these cells in the cortex was substantially less than in the descending thin limb (data not shown).


Hydration status affects osteopontin expression in the rat kidney
Light micrographs illustrating OPN immunostaining and in situ hybridization in the kidney from control (A–C), dehydrated (D–F) and hydrated (G–I) rats. The OPN immunostaining and hybridization signal increased remarkably in dehydrated animals, while it decreased in hydrated animals relative to control animals. OPN expression was primarily observed in the tubular profiles in the inner stripe of the outer medulla (ISOM). Note that the OPN immunostaining and hybridization signal were not only observed in the descending thin limb of Henle's loop (DTL), but also in the thick ascending limb (TAL) in dehydrated animals (E and F). Arrows indicate an abrupt transition from the OPN-negative proximal tubule (PT) to the OPN-positive descending thin limb of Henle's loop. Quantitative analysis of OPN protein and mRNA expression (J). OSOM, outer stripe of the outer medulla; IM, inner medulla. *p < 0.05 by two-tailed t-test versus control. Scale bars = 1 mm (G), 20 µm (H and I).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037293&req=5

Figure 2: Light micrographs illustrating OPN immunostaining and in situ hybridization in the kidney from control (A–C), dehydrated (D–F) and hydrated (G–I) rats. The OPN immunostaining and hybridization signal increased remarkably in dehydrated animals, while it decreased in hydrated animals relative to control animals. OPN expression was primarily observed in the tubular profiles in the inner stripe of the outer medulla (ISOM). Note that the OPN immunostaining and hybridization signal were not only observed in the descending thin limb of Henle's loop (DTL), but also in the thick ascending limb (TAL) in dehydrated animals (E and F). Arrows indicate an abrupt transition from the OPN-negative proximal tubule (PT) to the OPN-positive descending thin limb of Henle's loop. Quantitative analysis of OPN protein and mRNA expression (J). OSOM, outer stripe of the outer medulla; IM, inner medulla. *p < 0.05 by two-tailed t-test versus control. Scale bars = 1 mm (G), 20 µm (H and I).
Mentions: In control animals, OPN immunoreactivity was observed in the descending thin limb of Henle's loop in the inner stripe of the outer medulla (panel A in Fig. 2). Immunostaining was strongest in the initial part of the descending thin limb, continuous with the S3 segment of the proximal tubule (panel B in Fig. 2). Occasionally, faint immunostaining was observed in some proximal tubules and the parietal epithelium of Bowman's capsule (data not shown). Overall, the level of immunolabeling in these cells in the cortex was substantially less than in the descending thin limb (data not shown).

View Article: PubMed Central - PubMed

ABSTRACT

Osteopontin (OPN) is a secretory protein that plays an important role in urinary stone formation. Hydration status is associated with the development of urolithiasis. This study was conducted to examine the effects of dehydration and hydration on OPN expression in the rat kidney. Animals were divided into three groups, control, dehydrated, and hydrated. Kidney tissues were processed for light and electron microscope immunocytochemistry, in situ hybridization, and immunoblot analysis. Dehydration induced a significant increase in OPN protein expression, whereas increased fluid intake induced a decrease in protein expression. Under control conditions, OPN protein and mRNA expression were only detected in the descending thin limb (DTL). Dehydration induced increased expression in the DTL and the development of detectable expression in the thick ascending limb (TAL). In contrast, OPN expression levels declined to less than the controls in the DTL after hydration, while no expression of either protein or mRNA was detectable in the TAL. Immunoelectron microscopy demonstrated that hydration status altered tubular ultrastructure and intracellular OPN expression in the Golgi apparatus and secretory cytoplasmic vesicles. These data confirm that changes in oral fluid intake can regulate renal tubular epithelial cell OPN expression.

No MeSH data available.


Related in: MedlinePlus