International Urology and Nephrology 32: 215–218, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands. 215 N-acetyl-glucosaminidase (NAG) excretion in partially obstructed weanling rats M. De Gennaro 1 , M. Silveri 1 , M.L. Capitanucci 1 , A. Silvano 1 , F. Colistro 2 , A. Villani 3 & A. Zaccara 1 Departments of 1 Pediatric Surgery, 2 Biochemistry, and 3 Anesthesiology, Bambino Ges` u Children’s Hospital, Rome, Italy Abstract. The understanding of pathophysiology of obstructed uropathy has been facilitated by animal models with partial ureteric obstruction. Some studies on partially obstructed adult rats have drawn attention to a biphasic pattern of obstructive uropathy: an initial ‘destructive’ phase and a ‘steady’ phase in which renal deterioration no longer occurs and in which relief of obstruction would be of no advantage. We aimed to verify if this pattern applies also to younger (weanling) rats with more immature kidneys, resembling those of the human fetus. We measured the NAG-values in the urine samples of partially obstructed animals at different intervals of obstruction and in those of controls. The biphasic pattern proved to be the same as in adult rats as was previously documented, but the turning point occurred earlier (between 10 and 15 days of obstruction). Furthermore, there is evidence of low level values of N-Acetyl-Glucosaminidase (NAG) in the early phase of obstruction (5 days), demonstring that the increase of tubular enzyme is not due to the operation itself. There is evidence that, if the ‘destructive’ phase can be precisely identified by biochemical studies, this could help identifying those subjects who could benefit from relief of obstruction. Key words: Obstructive uropathy, N-acetyl-glucosaminidase (NAG), Weanling rats Introduction The technical refinements of antenatal diagnosis have brought about several studies aiming to understand the pathophysiology of obstructive uropathy. In this respect, several animal models have been designed, the most common and reproducible being those on guinea pigs [2], rabbits [12] and rats [5]. Most of these studies were based upon meticulous studies of histo- logy and renal function in partially obstructed animals before or after relief of obstruction. Although deteri- oration of renal function and parenchymal damage were well documented, very few biochemical data are currently available from obstructed kidneys, although they may detect very early changes in the renal paren- chyma. Interestingly, urinary biochemistry has been extensively studied in recent years in the human fetus [15–19]. Attention has been drawn to some urinary enzymes such as N-acetyl-glucosaminidase (NAG) [11–19] and β 2 microglobulin [23] as possible predictors of reversible or irreversible renal damage, in view of a possible vesico-amniotic shunt placement [9]. All these considerations gave rise to an experi- mental study designed to verify the reliability of NAG as a marker of obstructive uropathy in weanling (21 days old) rats. Materials and methods Weanling 3 week-old Sprague-Dawley rats (Università Cattolica, Rome, Italy) were used for the experiments. Fifty male animals were anaesthetized with intraab- dominal diazepam and intramuscular ketamine hydro- cloridrate. They were subsequently subjected to left partial ureteral obstruction according to Ulm & Miller [24]. The ureter was placed into a groove, made in the underlying psoas muscle. The edges were approxim- ated with 2 sutures (Ethilon 8–0, Ethicon Italia, Pratica