This study aims to determine if increased arginase activity contributes to endothelial dysfunction in chronic kidney disease (CKD). The researchers hypothesize that arginase activity will be increased in CKD rats compared to controls, leading to decreased nitric oxide production and impaired vasodilation. To test this, rats will undergo surgery to induce CKD. After 8-12 weeks, aortic and carotid rings will be isolated to assess vasodilation in response to acetylcholine with and without arginase inhibition. Arginase expression and activity will also be measured and compared between CKD and control rats. The results may provide insight into whether arginase inhibition can restore endothelial function in CKD.

1. The effects of arginase inhibition on
endothelial dysfunction in rats with
chronic kidney disease
Christopher R. Martens

2. Chronic Kidney Disease
• High prevalence in US
• Progressive Disease
Drop-off due to
• Stages I-V deaths from
CVD
• Low eGFR
• High Risk of CVD
• Endothelial Dysfunction
Coresh et. al, 2003

3. Endothelial Dysfunction
Decreased production or
bioavailability of nitric oxide
Shear Stress
NO

4. Endothelial Dysfunction
Arginase eNOS
Urea L-Arginine NO
Increased arginase activity could compete with
eNOS for substrate and reduce NO production

5. Arginase & Endothelial Dysfunction
Nitric Oxide Production
• Arginase activity ↑ with age
• ↓ NO Production
• ↑ Endothelial Dysfunction
• Restored with arginase
inhibition
Similar mechanism
in CKD? Kim et. al, 2009

6. Purpose & Hypothesis

7. Purpose & Hypothesis
• Is arginase expression or activity upregulated in CKD?
• Hypothesis: Arginase activity will be increased while expression with stay the
same

8. Purpose & Hypothesis
• Is arginase expression or activity upregulated in CKD?
• Hypothesis: Arginase activity will be increased while expression with stay the
same
• Does this increase contribute to endothelial dysfunction?
• Hypothesis: ↑ Arginase activity will result in ↓ NO production

9. Purpose & Hypothesis
• Is arginase expression or activity upregulated in CKD?
• Hypothesis: Arginase activity will be increased while expression with stay the
same
• Does this increase contribute to endothelial dysfunction?
• Hypothesis: ↑ Arginase activity will result in ↓ NO production
• Is endothelial function restored with arginase inhibition?
• Hypothesis: Acute arginase inhibition will restore vasodilation in vitro

10. Methods
• 20 Sprague Dawley Rats
• Male
• 12 Weeks Old
• CKD vs. SHAM (Control)
• Assessment of endothelial
function 8-12 weeks later

11. 5/6 Ablation/Infarction Surgery
• 2/3 ligation of left
kidney
• Complete removal
of left kidney
• Total=5/6 removal
or infarction of
renal mass

12. 5/6 Ablation/Infarction Surgery
Theatrical Version

13. Development of CKD
• Metabolic Cages
• Urine Creatinine
• Every 2 weeks
• Blood Draw
• Serum Creatinine

14. Isometric Ring Experiments
Thoracic aortas and carotid
arteries will be dissected
and prepared into 5mm
rings and loaded into a
myograph

15. Isometric Ring Experiments
Pre-Constriction
phenylephrine
~100mmHg
Vasorelaxation
acetylcholine

16. Isometric Ring Experiments
Pre-Constriction
phenylephrine
~100mmHg
Vasorelaxation
% Relaxation
0
acetylcholine 50
100
[Ach]

17. Isometric Ring Experiments
Pre-Constriction
phenylephrine
~100mmHg
Vasorelaxation
% Relaxation
0
Endothelial
acetylcholine 50
Dysfunction
100
[Ach]

18. Biochemical Analysis
• Protein Expression
• Western Blot
• Protein Activity
• Urea Production
• Citrulline
Production
Kim et. al, 2009

19. Statistical Analysis
• Vasorelaxation response
CKD SHAM
to acetylcholine will be
analyzed by a 2x2
ANOVA BEH
• Biochemical assays will Control
be analyzed using an un-
BEH = Arginase Inhibitor
paired t-test

20. Questions?