PhD student University of Georgia Athens, Georgia, United States
Abstract:
Background: The relationship between the intrarenal renin-angiotensin system (iRAS) and markers of the circulating renin-angiotensin-aldosterone system (cRAAS) in cats with chronic kidney disease (CKD) is understudied.
Objectives: To describe the correlation between iRAS and cRAAS markers in cats with surgically induced CKD. Animals: 11 purpose-bred cats with unilateral renal ischemia-induced CKD and an undisturbed (n=5) or nephrectomized (n=6) contralateral kidney; and 8 healthy cats. All cats were aged 0.6-2.4 years.
Methods: Observational case-control study. Serum and renal tissue equilibrium concentrations of angiotensin peptides and serum equilibrium concentrations of aldosterone were evaluated using liquid chromatography-tandem mass spectrometry. Renal transcription levels of angiotensin-converting enzyme (ACE), angiotensinogen (AGT), angiotensin II type 1 receptor (AT1R), and renin (REN) were quantified using reverse-transcription polymerase chain reaction. Data were log-transformed and correlations between each cRAAS and iRAS component were evaluated using Pearson correlation analysis.
Results: No correlation was found between circulating and tissular concentrations of angiotensin peptides (R=0.36 for angiotensin I; R=0.36 for angiotensin II; R=0.07 for angiotensin III). Circulating angiotensin II was positively correlated with renal transcription levels of AGT (R=0.51, p=0.045), circulating angiotensin I was positively correlated with renal angiotensin II (R=0.51, p=0.044), and circulating aldosterone was negatively correlated with renal transcription levels of ACE (R= -0.60, p=0.014). Conclusions and clinical importance: Equilibrium concentrations of circulating angiotensin peptides or aldosterone did not reflect those of renal tissular angiotensin peptides or ACE, AGT, AT1R, and REN transcription levels. Evaluation of the iRAS requires renal tissue specimens or the development of other non-invasive biomarker(s).
