Short Term Change of Urinary N-Acetyl-.BETA.-D-Glucosaminidase in Reduced Kidney Mass with Renal Artery Ligation

Abstract

ABSTRACT. The aim of the present study was to evaluate short term urinary NAG levels in a model of reduced kidney mass. The half and quarter kidney mass were made from ligation of the renal artery. Both groups decreased in the level of excreted NAG on day 1 and 2 after operation. On day 5 after operation, both groups achieved urinary enzyme levels comparable to that of the sham-operated group. The remaining compensated nephrons held normal range of excreted urinary NAG levels, although reduced number of nephrons resulted in a decline in urinary NAG levels. KEY WORDS: kidney function, renal disorder, urinary enzyme.J. Vet. Med. Sci. 68(12): 1355-1357, 2006 Urinary [9]. Serum creatinine has limited value in the detection of early renal damage, and thus urinary enzymes such as NAG are commonly used as markers for tubular injury. To date, there have been no studies on urinary NAG levels in reduced kidney mass. The aim of the study was to evaluate short term urinary NAG levels in a model of reduced kidney mass with renal artery ligation.The experiments were performed on 32 male SpragueDawley rats (Charles River Japan, Inc.), with a mean weight of 294 ± 11 g. Each rat was housed in a metabolism cage with controlled temperature (23°C) and relative humidity (52 ± 13%), and a synchronized 12-hr light/dark cycle. The rats were fed food and water ad libitum. Dietary intake and body weight were measured once daily.Prior to laparectomy, the rats were anesthetized with pentobarbital 40 mg/kg. The rats were assigned to sham operation (n=9), ligation of the right renal artery and vein (1/2 kidney; n=11), or ligation of the right renal artery and vein plus the left renal branch artery (1/4 kidney; n=12).Urine samples were collected for 4 days before operation as baseline samples and at 1-5, 12, and 19 days after operation. Urine volume was measured during each collection period. One ml of collected urine was centrifuged at 3,000 rpm for 5 min to obtain the supernatant, which was immediately stored at 4°C and used for measurement within 48 hr. At 3 days before operation and at 5, 12, and 19 days after operation, 1 ml of blood was collected from the subclavian vein under light anesthesia. The blood was centrifuged at 3,000 rpm for 5 min to obtain the supernatant, which was frozen and stored.The activity of urinary NAG was determined colorimetrically as the absorbance at 580 nm wavelength of m-cresol purple released by NAG from the substrate, sodio m-cresolsulfonphthaleinyl-N-acetyl-β-D-glucosaminide (MCP-NAG) (Shionogi & Co., Ltd., Tokyo, Japan). Serum and urine creatinine levels were measured with the Jáffe reaction method using a commercially available kit (Chugai Pharmaceutical Co., Ltd., Tokyo, Japan).Enzyme excretion (Eext) was calculated from measures of urinary enzyme activity (Eact) and urine volume (Uvol): Eext (U/kg) = Eact (U/l) × Uvol (ml)/kg body weight.The data collected at the different time points were analyzed for differences in body weight, water intake, food intake, urine volume, creatinine excretion, sodium ex...

N‐Acetyl‐β‐d‐Glucosaminidase Index as an Early Biomarker for Chronic Kidney Disease in Cats with Hyperthyroidism

“…A recent study evaluated this enzyme in a remnant kidney model in rats. 26 Initially, after renal artery ligation, NAG i decreased proportionately with nephron loss. After 5 days, compensatory mechanisms are thought to be responsible for increased NAG i to amounts present before ligation.…”

“…Cats with advanced CKD may have had an insufficient number of intact nephrons to release NAG from epithelial cells. A recent study evaluated this enzyme in a remnant kidney model in rats 26 . Initially, after renal artery ligation, NAG i decreased proportionately with nephron loss.…”