Measurement of aldosterone in feline, canine and human urine.
BACKGROUND
Systemic hypertension is an important problem in older cats associated with kidney disease and hypokalaemia, suggesting that excessive activity of the renin-angiotensin-aldosterone system might contribute to the hypertensive state. Fluctuations in plasma renin activity and plasma aldosterone concentrations complicate the interpretation of these assays.


OBJECTIVE
The aim of this study was to determine whether measurement of urinary aldosterone excretion in cats aided the investigation of hypertension.


METHODS
Urine concentrations of free (ethyl acetate extract) and 18-glucuronidated aldosterone (acid hydrolysis before extraction) were measured by radioimmunoassay in normal, normotensive and hypertensive azotaemic cats (n=11 per group). Urine samples from 11 healthy human volunteers and eight normal dogs were also analysed for comparison. Urinary aldosterone concentration was corrected for the urinary creatinine concentration.


RESULTS
Cats excreted 7.3 times less free aldosterone than human beings, and no free aldosterone was detected in dog urine. Acid hydrolysis led to large increases in aldosterone recovery from both human beings and dog but not feline urine. No significant effect of hypertension or azotaemia on feline urinary aldosterone concentration was found.


CONCLUSIONS
Measurement of aldosterone in feline urine using the available methodology has limited or no utility in investigating feline hypertension.
Syme
H M
HM
Department of Veterinary Clinical Sciences, The Royal Veterinary College, University of London, Royal College Street, London NW1 0TU.
Fletcher
M G R
MG
Bailey
S R
SR
Elliott
J
J
D000328:Adult; D000450:Aldosterone / Q000652:urine*; D000818:Animals; D002371:Cat Diseases / Q000175:diagnosis / Q000652:urine*; D002415:Cats; D004285:Dogs; D005260:Female; D006801:Humans; D006977:Hypertension, Renal / Q000175:diagnosis / Q000652:urine / Q000662:veterinary*; D008297:Male; D013045:Species Specificity
D000450:Aldosterone