Post hoc comparison of the intrarenal and circulating renin-angiotensin(-aldosterone) systems in cats with ischemia-induced chronic kidney disease.

Activities of the circulating and intrarenal renin-angiotensin(-aldosterone) systems (RA[A]S) are incompletely understood in people and cats with chronic kidney disease (CKD). We measured circulating and intrarenal RA(A)S markers in healthy cats (n = 8) and cats with induced CKD (n = 6 subjected to unilateral renal ischemia [RI group] and n = 5 subjected to RI and delayed contralateral nephrectomy [RI-DCN group]). Serum equilibrium concentrations of angiotensin peptides and aldosterone, plasma renin activity, and urinary aldosterone-to-creatinine ratio were evaluated before and after renal injury in CKD cats and at a single timepoint in healthy cats. Renal tissular concentrations of angiotensin peptides and mRNA levels of RA(A)S-related genes were measured in all cats. There was no significant correlation between circulating angiotensin peptide concentrations and their respective renal concentrations. Intrarenal angiotensin I concentrations and AGT transcript levels were positively correlated, and ACE transcript levels were negatively correlated with serum creatinine concentration. Circulating RA(A)S markers were not different between healthy and CKD groups, except for serum angiotensin 1-5, which was lower in the RI group compared to the healthy group. Intrarenal angiotensin peptide concentrations did not differ among groups. Compared to healthy cats, mRNA levels of ACE, AT1R, and REN were lower, and AGT levels were higher in one or both CKD group(s).