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The role of nitric oxide in the dysregulation of the urine concentration mechanism in diabetes mellitus.

Cipriani P, Kim SL, Klein JD, Sim JH, von Bergen TN, Blount MA - Front Physiol (2012)

Bottom Line: We examined how lack of NO affects the transporters involved in urine concentration in diabetic animals.UT-A1 and UT-A3 were significantly increased in diabetic rat inner medulla.Our studies found that although diabetic-induced glycosylation remained increased, total protein expression was decreased to control levels in diabetic rats treated with L-NAME.

View Article: PubMed Central - PubMed

Affiliation: Renal Division, Department of Medicine, Emory University Atlanta, GA, USA.

ABSTRACT
Uncontrolled diabetes mellitus results in osmotic diuresis. Diabetic patients have lowered nitric oxide (NO) which may exacerbate polyuria. We examined how lack of NO affects the transporters involved in urine concentration in diabetic animals. Diabetes was induced in rats by streptozotocin. Control and diabetic rats were given L-NAME for 3 weeks. Urine osmolality, urine output, and expression of urea and water transporters and the Na-K-2Cl cotransporter were examined. Predictably, diabetic rats presented with polyuria (increased urine volume and decreased urine osmolality). Although metabolic parameters of control rats were unaffected by L-NAME, treated diabetic rats produced 30% less urine and osmolality was restored. UT-A1 and UT-A3 were significantly increased in diabetic rat inner medulla. While L-NAME treatment alone did not alter UT-A1 or UT-A3 abundance, absence of NO prevented the upregulation of both transporters in diabetic rats. Similarly, AQP2 and NKCC2 abundance was increased in diabetic animals however, expression of these transporters were unchanged by L-NAME treatment of diabetes. Increased expression of the concentrating transporters observed in diabetic rats provides a compensatory mechanism to decrease solute loss despite persistent glycosuria. Our studies found that although diabetic-induced glycosylation remained increased, total protein expression was decreased to control levels in diabetic rats treated with L-NAME. While the role of NO in urine concentration remains unclear, lowered NO associated with diabetes may be deleterious to the transporters' response to the subsequent osmotic diuresis.

No MeSH data available.


Related in: MedlinePlus

Upregulation of glycosylated AQP2 in diabetes is blunted by NO inhibition. Displayed is a representative western blot of IM tip (A) and base (D) probed for AQP2. Densitometry was determined for the glycosylated (B) and unglycosylated forms (C) in the IM tip as well as the glycosylated (E) and unglycosylated forms (F) in the IM base. To prevent saturation of bands, the blot was scanned at a lighter intensity to measure glycosylated AQP2 (A,D) and at a higher intensity to measure the unglycosylated AQP2 (A,D) however, images are gleaned from the same representative western blot. The experimental conditions were performed five times (n = 5) where there were five animals per experimental group in each cohort. In total, 25 animals per experimental group were analyzed. *p < 0.05 compared to control, †p < 0.05 compared to DM.
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Figure 3: Upregulation of glycosylated AQP2 in diabetes is blunted by NO inhibition. Displayed is a representative western blot of IM tip (A) and base (D) probed for AQP2. Densitometry was determined for the glycosylated (B) and unglycosylated forms (C) in the IM tip as well as the glycosylated (E) and unglycosylated forms (F) in the IM base. To prevent saturation of bands, the blot was scanned at a lighter intensity to measure glycosylated AQP2 (A,D) and at a higher intensity to measure the unglycosylated AQP2 (A,D) however, images are gleaned from the same representative western blot. The experimental conditions were performed five times (n = 5) where there were five animals per experimental group in each cohort. In total, 25 animals per experimental group were analyzed. *p < 0.05 compared to control, †p < 0.05 compared to DM.

Mentions: AQP2 is expressed as glycosylated (40–46-kDa) and unglycosylated (29-kDa) proteins (Nejsum et al., 2001) as observed in control rat IM tip and base (Figures 3A,D). l-NAME treatment did not affect AQP2 expression in the papilla but did lower protein levels in the IM base (Figures 3B,E). Glycosylated AQP2 protein levels were significantly increased in both the tip and base of diabetic IM (Figures 3B,E); however, the unglycosylated form of AQP2 was not altered in response to diabetes in either IM tip or base (Figures 3C,F). In the IM tip of diabetic animals, l-NAME treatment had no effect on the unglycosylated AQP2 expression (Figure 3C) but did reduce the glycosylated AQP2 abundance to basal level (Figure 3B). l-NAME treatment of DM animals lowered glycosylated AQP2 levels in the IM base compared to DM animals (Figure 3E) but did not alter unglycosylated AQP2 abundance (Figure 3F).


The role of nitric oxide in the dysregulation of the urine concentration mechanism in diabetes mellitus.

Cipriani P, Kim SL, Klein JD, Sim JH, von Bergen TN, Blount MA - Front Physiol (2012)

Upregulation of glycosylated AQP2 in diabetes is blunted by NO inhibition. Displayed is a representative western blot of IM tip (A) and base (D) probed for AQP2. Densitometry was determined for the glycosylated (B) and unglycosylated forms (C) in the IM tip as well as the glycosylated (E) and unglycosylated forms (F) in the IM base. To prevent saturation of bands, the blot was scanned at a lighter intensity to measure glycosylated AQP2 (A,D) and at a higher intensity to measure the unglycosylated AQP2 (A,D) however, images are gleaned from the same representative western blot. The experimental conditions were performed five times (n = 5) where there were five animals per experimental group in each cohort. In total, 25 animals per experimental group were analyzed. *p < 0.05 compared to control, †p < 0.05 compared to DM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3368392&req=5

Figure 3: Upregulation of glycosylated AQP2 in diabetes is blunted by NO inhibition. Displayed is a representative western blot of IM tip (A) and base (D) probed for AQP2. Densitometry was determined for the glycosylated (B) and unglycosylated forms (C) in the IM tip as well as the glycosylated (E) and unglycosylated forms (F) in the IM base. To prevent saturation of bands, the blot was scanned at a lighter intensity to measure glycosylated AQP2 (A,D) and at a higher intensity to measure the unglycosylated AQP2 (A,D) however, images are gleaned from the same representative western blot. The experimental conditions were performed five times (n = 5) where there were five animals per experimental group in each cohort. In total, 25 animals per experimental group were analyzed. *p < 0.05 compared to control, †p < 0.05 compared to DM.
Mentions: AQP2 is expressed as glycosylated (40–46-kDa) and unglycosylated (29-kDa) proteins (Nejsum et al., 2001) as observed in control rat IM tip and base (Figures 3A,D). l-NAME treatment did not affect AQP2 expression in the papilla but did lower protein levels in the IM base (Figures 3B,E). Glycosylated AQP2 protein levels were significantly increased in both the tip and base of diabetic IM (Figures 3B,E); however, the unglycosylated form of AQP2 was not altered in response to diabetes in either IM tip or base (Figures 3C,F). In the IM tip of diabetic animals, l-NAME treatment had no effect on the unglycosylated AQP2 expression (Figure 3C) but did reduce the glycosylated AQP2 abundance to basal level (Figure 3B). l-NAME treatment of DM animals lowered glycosylated AQP2 levels in the IM base compared to DM animals (Figure 3E) but did not alter unglycosylated AQP2 abundance (Figure 3F).

Bottom Line: We examined how lack of NO affects the transporters involved in urine concentration in diabetic animals.UT-A1 and UT-A3 were significantly increased in diabetic rat inner medulla.Our studies found that although diabetic-induced glycosylation remained increased, total protein expression was decreased to control levels in diabetic rats treated with L-NAME.

View Article: PubMed Central - PubMed

Affiliation: Renal Division, Department of Medicine, Emory University Atlanta, GA, USA.

ABSTRACT
Uncontrolled diabetes mellitus results in osmotic diuresis. Diabetic patients have lowered nitric oxide (NO) which may exacerbate polyuria. We examined how lack of NO affects the transporters involved in urine concentration in diabetic animals. Diabetes was induced in rats by streptozotocin. Control and diabetic rats were given L-NAME for 3 weeks. Urine osmolality, urine output, and expression of urea and water transporters and the Na-K-2Cl cotransporter were examined. Predictably, diabetic rats presented with polyuria (increased urine volume and decreased urine osmolality). Although metabolic parameters of control rats were unaffected by L-NAME, treated diabetic rats produced 30% less urine and osmolality was restored. UT-A1 and UT-A3 were significantly increased in diabetic rat inner medulla. While L-NAME treatment alone did not alter UT-A1 or UT-A3 abundance, absence of NO prevented the upregulation of both transporters in diabetic rats. Similarly, AQP2 and NKCC2 abundance was increased in diabetic animals however, expression of these transporters were unchanged by L-NAME treatment of diabetes. Increased expression of the concentrating transporters observed in diabetic rats provides a compensatory mechanism to decrease solute loss despite persistent glycosuria. Our studies found that although diabetic-induced glycosylation remained increased, total protein expression was decreased to control levels in diabetic rats treated with L-NAME. While the role of NO in urine concentration remains unclear, lowered NO associated with diabetes may be deleterious to the transporters' response to the subsequent osmotic diuresis.

No MeSH data available.


Related in: MedlinePlus