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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 UT-A1 in diabetes is blunted by NO inhibition. Shown is a representative western blot of inner medulla (IM) tip (A) and base (D) probed for UT-A1 where each lane represents one rat. Densitometry was determined for the 97-kDa (B) and 117-kDa glyco-forms (C) in IM tip and the 97-kDa (E) and 117-kDa glyco-forms (F) in IM base. The experimental conditions were performed 5 times (n = 5) where there were 5 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 1: Upregulation of UT-A1 in diabetes is blunted by NO inhibition. Shown is a representative western blot of inner medulla (IM) tip (A) and base (D) probed for UT-A1 where each lane represents one rat. Densitometry was determined for the 97-kDa (B) and 117-kDa glyco-forms (C) in IM tip and the 97-kDa (E) and 117-kDa glyco-forms (F) in IM base. The experimental conditions were performed 5 times (n = 5) where there were 5 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: UT-A1, a glycoprotein, is expressed in both the papilla and IM base. Although the functional difference remains a mystery, abundance of the two glycoproteins of UT-A1 (117 and 97-kDa) differ based on tissue location. Western analysis of control rats detected both glyco-forms of UT-A1 in the IM tip (Figure 1A) and the predominant 97-kDa form in IM base (Figure 1D). l-NAME treatment alone did not change the total protein abundance of UT-A1 in either section of the IM nor did the inhibition of NO change the glycosylation state (Figure 1). UT-A1 expression was significantly upregulated in both the IM tip and base of diabetic rats. This was largely attributable to increased expression of the 117-kDa form (Figures 1C,F). Diabetic rats treated with l-NAME did not have a significant increase in total UT-A1 protein abundance (97- or 117-kDa) in the IM tip (Figures 1B,C). In the IM base of l-NAME-treated diabetic animals, 97-kDa UT-A1 abundance was statistically increased when compared to control rats but expression of this glycoprotein was also significantly decreased compared to diabetic rats (Figure 1E). l-NAME treatment of diabetic animals did inhibit induction of the 117-kDa form of UT-A1 however the amount of 117-kDa protein is ∼3.5-fold over basal levels (Figure 1F).


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 UT-A1 in diabetes is blunted by NO inhibition. Shown is a representative western blot of inner medulla (IM) tip (A) and base (D) probed for UT-A1 where each lane represents one rat. Densitometry was determined for the 97-kDa (B) and 117-kDa glyco-forms (C) in IM tip and the 97-kDa (E) and 117-kDa glyco-forms (F) in IM base. The experimental conditions were performed 5 times (n = 5) where there were 5 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 1: Upregulation of UT-A1 in diabetes is blunted by NO inhibition. Shown is a representative western blot of inner medulla (IM) tip (A) and base (D) probed for UT-A1 where each lane represents one rat. Densitometry was determined for the 97-kDa (B) and 117-kDa glyco-forms (C) in IM tip and the 97-kDa (E) and 117-kDa glyco-forms (F) in IM base. The experimental conditions were performed 5 times (n = 5) where there were 5 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: UT-A1, a glycoprotein, is expressed in both the papilla and IM base. Although the functional difference remains a mystery, abundance of the two glycoproteins of UT-A1 (117 and 97-kDa) differ based on tissue location. Western analysis of control rats detected both glyco-forms of UT-A1 in the IM tip (Figure 1A) and the predominant 97-kDa form in IM base (Figure 1D). l-NAME treatment alone did not change the total protein abundance of UT-A1 in either section of the IM nor did the inhibition of NO change the glycosylation state (Figure 1). UT-A1 expression was significantly upregulated in both the IM tip and base of diabetic rats. This was largely attributable to increased expression of the 117-kDa form (Figures 1C,F). Diabetic rats treated with l-NAME did not have a significant increase in total UT-A1 protein abundance (97- or 117-kDa) in the IM tip (Figures 1B,C). In the IM base of l-NAME-treated diabetic animals, 97-kDa UT-A1 abundance was statistically increased when compared to control rats but expression of this glycoprotein was also significantly decreased compared to diabetic rats (Figure 1E). l-NAME treatment of diabetic animals did inhibit induction of the 117-kDa form of UT-A1 however the amount of 117-kDa protein is ∼3.5-fold over basal levels (Figure 1F).

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