PLASMA-RENIN ACTIVITY AND ANGIOTENSIN-I AND ALDOSTERONE CONCENTRATIONS IN CATS WITH HYPERTENSION ASSOCIATED WITH CHRONIC RENAL-DISEASE

Objective-To determine plasma renin activity (PRA), angiotensin I (Ang I), and aldosterone (ALDO) values in clinically normal cats and hyper tensive cats with renal disease, and the relation of renin-angiotensin -aldosterone activation in response to treatment with beta-blockers or angiotensin-converting enzyme inhibitors. Animals-5 normotensive heal thy control cats and 12 untreated hypertensive cats with chronic renal disease. Procedure-Untreated hypertensive cats received either propra nolol (n = 6) or enalapril (n = 6) as initial antihypertensive treatme nt. PRA and baseline plasma Ang I and ALDO concentrations were measure d prior to treatment. The difference in Ang I values at 2 hours (Ang I generated) and at time 0 (baseline Ang I) was divided by 2 to give th e PRA value. Values for PRA, Ang I, and ALDO were obtained from 5 clin ically normal, normotensive cats, and compared with those of hypertens ive cats. Results-Mean +/- SD PRA and baseline Ang I concentration wer e not significantly different between normotensive and hypertensive ca ts. Mean ALDO concentration was significantly (P = 0.0235) higher in h ypertensive cats with renal disease (186.18 +/- 145.15 pg/ml), compare d with that in normotensive controls (51.1 +/- 16.76 pg/ml). Eight hyp ertensive cats with ALDO concentration > 2 SD above the mean concentra tion in control cats had low (n = 3), normal (n = 4), or high (n = 1) PRA, suggesting variable activation of the renin-angiotensin-aldostero ne axis in the hypertensive state. Overall, enalapril was effective lo ng-term monotherapy in only 1 of 6 cats, and propranolol was ineffecti ve as long-term monotherapy. Clinical Relevance-Evaluation of the reni n-angiotensin-aldosterone system in cats with hypertension associated with renal disease may lead to greater understanding of the pathophysi ologic mechanisms of this disorder. In addition, identification of bio chemical markers in hypertensive cats may permit selection of appropri ate antihypertensive drugs. Propranolol and enalapril were ineffective antihypertensive agents in most cats of this study.