Comparative study of alanine-amino-peptidase and gamma-glutamyl-transferase activity in normal Wistar rat urine

Age-dependent enzymuria, proteinuria and changes in renal blood flow and glomerular filtration rate in rats

The time course of urinary excretion of two enzymatic indicators of renal damage, N-acetyl-beta-D-glucosaminidase (NAG) and alanine aminopeptidase (AAP) was measured in female Wistar rats at different ages. NAG and AAP are localized at different sites of the nephron and are released into the urine when kidney damage occurs. Total protein flow, urinary volume and creatinine flow were also determined. In a parallel experiment, the effect of aging on renal blood flow (RBF) and glomerular filtration rate (GFR) was examined in young (1.5-month) adult (3-month) and elderly (20-month) female rats. Clearance following a single injection of [131I]o-iodohippurate (hippuran, OIH) was used for the measurement of effective RBF and as an index of tubular cell function. [125I]Iothalamate (IOT) clearance was used to measure GFR. With advancing age, an increase in NAG and AAP urinary flow appeared. The increases in protein excretion were greater than and previous to those of enzyme excretion. It is shown that absolute RBF and GFR (ml/min) in old rats are greater than in young or adult animals. When absolute RBF or GFR was divided by kidney weight (ml/min/g) no clearance changes appeared in any age group studied; only when clearance was expressed in relation to body weight (ml/min/100 g), a decrease in RBF and GFR was evidenced. This indicates that the rate of increase of both RBF and GFR with age is similar to that of kidney weight and lower than that of body weight. The present findings indicate that urinary markers of renal injury increase with age, whereas GFR and RBF only decrease when expressed as clearance related to body weight.

Excretion of urinary enzymes in female Sprague-Dawley rats in relation to cellular compartment, creatinine excretion and diuresis

One hundred and one young-adult female Sprague-Dawley rats were acclimatized to metabolic cages for 2 days. After that time 24-hour urine was collected at a constant cooling temperature of 0-4 degrees C. After gel filtration the enzyme activities were determined, and the resulting values were used to calculate 24-hour excretions. The following reference ranges (2.5 and 97.5 percentiles) were determined (in mU/24 h): lactate dehydrogenase 43-181; phosphohexoseisomerase 45-1445; glutathione-S-transferase 1-299; alkaline phosphatase 27-1239; leucine arylamidase 72-377; gamma-glutamyltransferase 1334-9188; arylsulphatase A 59-309; beta-galactosidase 76-305; beta-glucuronidase 20-2756; beta-N-acetyl-D-glucosaminidase 66-491; glutamate dehydrogenase 7-711. There was a significant (though not very high) correlation with diuresis for the lysosomal enzymes beta-N-acetyl-D-glucosaminidase, arylsulphatase A and beta-galactosidase, and for glutamate dehydrogenase, lactate dehydrogenase, phosphohexoseisomerase and alkaline phosphatase. The relation to creatinine excretion was markedly close for the lysosomal enzymes beta-N-acetyl-D-glucosaminidase, arylsulphatase A and beta-galactosidase (r = 0.71-0.83), as well as for alkaline phosphatase, leucine arylamidase and gamma-glutamyltransferase. There was a relatively high correlation between the excretion of beta-N-acetyl-D-glucosaminidase, arylsulphatase A and beta-galactosidase among themselves (r = 0.63-0.81) as well as between leucine arylamidase and gamma-glutamyltransferase (r = 0.75).