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Impaired epithelial Na+ channel activity contributes to cystogenesis and development of autosomal recessive polycystic kidney disease in PCK rats.

Pavlov TS, Levchenko V, Ilatovskaya DV, Palygin O, Staruschenko A - Pediatr. Res. (2014)

Bottom Line: ENaC and aquaporin-2 expression and ENaC activity were tested with immunohistochemistry and patch-clamp electrophysiology, respectively.In contrast, the 12 wk of treatment with the loop diuretic furosemide had no effect on cystogenesis.Immunohistochemical analysis confirmed that β-ENaC and aquaporin-2 expressions in cysts are decreased compared with nondilated tubules from PCK rat kidneys.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin.

ABSTRACT

Background: Autosomal recessive polycystic kidney disease is a genetic disorder characterized by the development of renal cysts of tubular epithelial cell origin. Epithelial Na(+) channel (ENaC) is responsible for sodium reabsorption in the aldosterone-sensitive distal nephron. Here, we investigated the ENaC expression and activity in cystic tissue taken from rats with autosomal recessive polycystic kidney disease.

Methods: Polycystic kidney (PCK) rats were treated with the selective ENaC inhibitor benzamil given in the drinking water, and after 4 or 12 wk, the severity of morphological malformations in the kidneys was assessed. ENaC and aquaporin-2 expression and ENaC activity were tested with immunohistochemistry and patch-clamp electrophysiology, respectively.

Results: Treatment with benzamil exacerbated development of cysts compared with the vehicle-treated animals. In contrast, the 12 wk of treatment with the loop diuretic furosemide had no effect on cystogenesis. Single-channel patch-clamp analysis revealed that ENaC activity in the freshly isolated cystic epithelium was significantly lower than that in the noncystic collecting ducts isolated from PCK or normal Sprague-Dawley rats. Immunohistochemical analysis confirmed that β-ENaC and aquaporin-2 expressions in cysts are decreased compared with nondilated tubules from PCK rat kidneys.

Conclusion: We demonstrated that cystic epithelium exhibits low ENaC activity and this phenomenon can contribute to cyst progression.

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Inhibition of ENaC results in the progression of cyst formation in PCK rats. (a) Morphology of the kidneys collected from PCK rats after 4 or 12 weeks treatment with benzamil (benza) or vehicle (control). Scale bar is 5 mm. (b) Kidney weight/total body weight (TBW) ratios were calculated and graphed as a percentage. (c) Cysts area, % of total slice. Kidney sections were morphometrically analyzed as described in Materials and Methods to determine the surface area of the remaining kidney tissue relative to the cyst space. N = 6 rats in each group. *p<0.05 vs vehicle-control.
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Figure 1: Inhibition of ENaC results in the progression of cyst formation in PCK rats. (a) Morphology of the kidneys collected from PCK rats after 4 or 12 weeks treatment with benzamil (benza) or vehicle (control). Scale bar is 5 mm. (b) Kidney weight/total body weight (TBW) ratios were calculated and graphed as a percentage. (c) Cysts area, % of total slice. Kidney sections were morphometrically analyzed as described in Materials and Methods to determine the surface area of the remaining kidney tissue relative to the cyst space. N = 6 rats in each group. *p<0.05 vs vehicle-control.

Mentions: Amiloride and its derivatives (e.g. benzamil) have been long used as potassium-sparing diuretics that block sodium reabsorption through ENaC, and thus have potent antihypertensive effects, especially in such states of ENaC activation as in Liddle's syndrome (4). Here we used PCK rats to investigate the effects of benzamil at different stages of the disease to determine whether ENaC inhibitors modulate cyst formation. Benzamil (15 mg/L) was administered in drinking water to 4 week old PCK rats for either 4 or 12 weeks. As demonstrated by our data, benzamil aggravates cyst formation in PCK rats (Figure 1). After 4 weeks of treatment, kidney/body weight ratio was not different between the groups, whereas by week 12, benzamil-treated rats developed severe renal hypertrophy as measured by kidneys/total body weight ratio. Cyst progression in benzamil-treated rats was significantly higher than in the control groups after both 4 and 12 weeks of treatment. Therefore, we conclude that ENaC-mediated sodium absorption plays a critical role in cystogenesis in ARPKD.


Impaired epithelial Na+ channel activity contributes to cystogenesis and development of autosomal recessive polycystic kidney disease in PCK rats.

Pavlov TS, Levchenko V, Ilatovskaya DV, Palygin O, Staruschenko A - Pediatr. Res. (2014)

Inhibition of ENaC results in the progression of cyst formation in PCK rats. (a) Morphology of the kidneys collected from PCK rats after 4 or 12 weeks treatment with benzamil (benza) or vehicle (control). Scale bar is 5 mm. (b) Kidney weight/total body weight (TBW) ratios were calculated and graphed as a percentage. (c) Cysts area, % of total slice. Kidney sections were morphometrically analyzed as described in Materials and Methods to determine the surface area of the remaining kidney tissue relative to the cyst space. N = 6 rats in each group. *p<0.05 vs vehicle-control.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4268054&req=5

Figure 1: Inhibition of ENaC results in the progression of cyst formation in PCK rats. (a) Morphology of the kidneys collected from PCK rats after 4 or 12 weeks treatment with benzamil (benza) or vehicle (control). Scale bar is 5 mm. (b) Kidney weight/total body weight (TBW) ratios were calculated and graphed as a percentage. (c) Cysts area, % of total slice. Kidney sections were morphometrically analyzed as described in Materials and Methods to determine the surface area of the remaining kidney tissue relative to the cyst space. N = 6 rats in each group. *p<0.05 vs vehicle-control.
Mentions: Amiloride and its derivatives (e.g. benzamil) have been long used as potassium-sparing diuretics that block sodium reabsorption through ENaC, and thus have potent antihypertensive effects, especially in such states of ENaC activation as in Liddle's syndrome (4). Here we used PCK rats to investigate the effects of benzamil at different stages of the disease to determine whether ENaC inhibitors modulate cyst formation. Benzamil (15 mg/L) was administered in drinking water to 4 week old PCK rats for either 4 or 12 weeks. As demonstrated by our data, benzamil aggravates cyst formation in PCK rats (Figure 1). After 4 weeks of treatment, kidney/body weight ratio was not different between the groups, whereas by week 12, benzamil-treated rats developed severe renal hypertrophy as measured by kidneys/total body weight ratio. Cyst progression in benzamil-treated rats was significantly higher than in the control groups after both 4 and 12 weeks of treatment. Therefore, we conclude that ENaC-mediated sodium absorption plays a critical role in cystogenesis in ARPKD.

Bottom Line: ENaC and aquaporin-2 expression and ENaC activity were tested with immunohistochemistry and patch-clamp electrophysiology, respectively.In contrast, the 12 wk of treatment with the loop diuretic furosemide had no effect on cystogenesis.Immunohistochemical analysis confirmed that β-ENaC and aquaporin-2 expressions in cysts are decreased compared with nondilated tubules from PCK rat kidneys.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin.

ABSTRACT

Background: Autosomal recessive polycystic kidney disease is a genetic disorder characterized by the development of renal cysts of tubular epithelial cell origin. Epithelial Na(+) channel (ENaC) is responsible for sodium reabsorption in the aldosterone-sensitive distal nephron. Here, we investigated the ENaC expression and activity in cystic tissue taken from rats with autosomal recessive polycystic kidney disease.

Methods: Polycystic kidney (PCK) rats were treated with the selective ENaC inhibitor benzamil given in the drinking water, and after 4 or 12 wk, the severity of morphological malformations in the kidneys was assessed. ENaC and aquaporin-2 expression and ENaC activity were tested with immunohistochemistry and patch-clamp electrophysiology, respectively.

Results: Treatment with benzamil exacerbated development of cysts compared with the vehicle-treated animals. In contrast, the 12 wk of treatment with the loop diuretic furosemide had no effect on cystogenesis. Single-channel patch-clamp analysis revealed that ENaC activity in the freshly isolated cystic epithelium was significantly lower than that in the noncystic collecting ducts isolated from PCK or normal Sprague-Dawley rats. Immunohistochemical analysis confirmed that β-ENaC and aquaporin-2 expressions in cysts are decreased compared with nondilated tubules from PCK rat kidneys.

Conclusion: We demonstrated that cystic epithelium exhibits low ENaC activity and this phenomenon can contribute to cyst progression.

Show MeSH
Related in: MedlinePlus