Infradian biorhythms of enzymuria in man?

The temporal courses of dipeptidyl peptidase IV gamma-glutamyltransferase and alanine aminopeptidase were followed over 70 days in the morning urine of 15 healthy persons. Subsequent to basic statistical analysis a two-step procedure was performed, including spectral analysis and the fit of a cosine function by non-linear regression. The excretion of the 3 enzymes followed an infradian biorhythm with a mean period length of 10.04 for dipeptidyl peptidase IV, 13.34 for gamma-glutamyltransferase and 10.17 for alanine aminopeptidase. In addition to the basic rhythmic process described by the fitted cosine functions, in most of the enzyme patterns steap peaks of very high excretory activity appeared which was verified in repeated measurements. These infradian biorhythms with changes in the range of 100% and more, as well as their interindividual variations, have to be considered in assessing the excretion of enzymes.

Induction of light hydrocarbon nephropathy by p-dichlorobenzene

In order to clarify the etiology of a dose-related increase in the incidence of tubular cell adenocarcinomas of the kidney in male rats, the nephrotoxicity of p-dichlorobenzene (p-DCB) was investigated in a subchronic study. Groups of ten male and ten female Fischer 344 rats were dosed by gavage with 0 (controls), 75, 150, 300 or 600 mg p-DCB/kg/day in corn oil. Half of the animals were sacrificed after 4 weeks and the remainder after 13 weeks. Increased urinary LDH and epithelial cell excretion and exacerbation of hyaline droplet accumulation in the cytoplasm of renal cortical cells were observed in male rats over the entire dose range investigated. Tubular single cell necrosis, dilated tubules with granular cast formation in the outer zone of the medulla, were evident in male rats after 4 and 13 weeks of treatment with doses of 150-600 mg/kg/day. In female rats there was no indication of a nephrotoxic action of p-DCB. The effects on the kidney, both in their morphological characteristics and the fact that they occur exclusively in male animals, correspond to the light hydrocarbon nephropathy observed as a result of short-term treatment with a number of aliphatic and cyclic hydrocarbons. The development of cortical renal tumors seems to be associated with this kind of kidney damage which is unique to male rats. The literature on this subject generally regards these renal effects as not predictive for man.

Urinary alanine aminopeptidase assay improved as result of multivariate response-surface analysis

Optimization of determination of alanine aminopeptidase in urine by univariate study led to a method involving pretreatment of urine with Sephadex G50. Re-examination of the optimization by multivariate study led us to recommend higher optimal concentrations: 5.8 mmol/L for the substrate and 300 mmol/L for the Tris buffer. Under these new conditions, pretreatment of urine was no longer necessary and the assay could be completely automated.

[Demonstration of seasonal variations of circadian rhythm in gentamicin-induced chrono-nephrotoxicity in rats]

The present study investigates the chronobiological approach of the gentamicin-induced nephrotoxicity in rats treated with a single sublethal dose administered at different times of day and season of year. The nephrotoxicity is appreciated by gamma-glutamyl-transferase and alanine-amino-peptidase, two enzymes of the brush border cells and N-acetyl-beta-D-glucosaminidase, a lysosomal enzyme. These excretions peak out at 8 p.m. and reach a through at 8 a.m. for the experimentation in january-february. In contrast, for the experimentation in June-July, we evidence gamma-glutamyl-transferase and alanine aminopeptidase excretion increased at 2 p.m. and decreased at 8 p.m. So, we evidence with gentamicin not only a circadian but also a seasonal susceptibility in rats.

Urinary enzymes and low-molecular-mass proteins as indicators of diabetic nephropathy

We measured the excretion rates of six urinary enzymes that either originate from the proximal renal tubule, like alanine aminopeptidase (EC 3.4.11.2), alkaline phosphatase (EC 3.1.3.1), gamma-glutamyltransferase (EC 2.3.2.2), and N-acetyl-beta-D-glucosaminidase (EC 3.2.1.30), or that are typical low-molecular-mass proteins, like lysozyme (EC 3.2.1.17) and pancreatic ribonuclease (EC 3.1.27.5). These rates were compared with those of total protein and albumin in urine of 36 insulin-dependent diabetic men and 30 healthy men. Seventeen of the diabetics had "clinical proteinuria," defined as excretion of more than 7.5 g of protein per mole of urinary creatinine (group B). Group A comprised the 19 diabetics without proteinuria. Except for gamma-glutamyltransferase, the excretions of enzymes and proteins were significantly higher in diabetics than in controls and were greater in group B than in group A. N-Acetyl-beta-D-glucosaminidase was the analyte most often increased in group A (89%), followed by albumin and alkaline phosphatase (each 32%). All patients in group B showed increased excretion of N-acetyl-beta-D-glucosaminidase. We conclude from the comparative data that this enzyme may be useful as an early predictor of diabetic nephropathy.

[Evaluation of damage in subjects exposed to nephrotoxic substances]

Nephritic functionality has been studies, making use of same nephritic enzymes dosage (NAG, AAP, alpha-glucosidase, lysozyme) in three groups of workers (varnishers, metallurgists, plastic manufacture employees) professionally exposed to nephritic damage, and in a control group made up of not professionally exposed to the same hazard subjects. The aim was to precociously detect possible nephritic damage, i.e. before classic nephritic functionality indexes were distorted. An increased enzymuria appeared in those subjects that were exposed to nephrotoxic hazard. Increased enzymuria have been found in only one subject of the control group. We deem it should be useful, to customarily measure out nephritic enzymes as trusted index of tabular damage, in hiring and pensionary control examinations.

Circadian variations in the renal toxicity of gentamicin in rats

The hypothesis that sublethal doses of aminoglycosides cause renal tubule disorders resulting in changes of urine enzyme levels was investigated. The renal status following injection of a single sublethal dose of gentamicin (200 mg/kg) at different times during a 24 h cycle was studied. Increased excretion of gamma-glutamyl transferase, alanine aminopeptidase and N-acetyl-beta-D-glucosaminidase, used clinically as markers for tubule toxicity of aminoglycosides, was maximal when gentamicin was administered to rats at 2 p.m. and was minimal when injected at 8 p.m. These significant differences in enzyme excretion as a function of injection time are correlated with the concentration of gentamicin in the urine and in the renal cortex.

Urinary enzyme excretion after donor nephrectomy

A number of recent studies of long-term kidney donors have reviewed glomerular function and blood pressure. Little attention has been paid to the potentially damaging effects of compensatory hyperfiltration on renal tubular cells after donor nephrectomy. The urinary excretion of high-molecular-weight enzymes is a sensitive indicator of renal tubular cell damage. This study compares the urinary excretion of four enzymes (alanine aminopeptidase, alkaline phosphatase, N-acetyl-beta-D-glucosaminidase, and lactate dehydrogenase) in a group of 77 subjects who had undergone unilateral nephrectomy up to 21 years previously with 52 healthy non-nephrectomized controls. The urinary excretion for all four enzymes by the remaining kidney after contralateral nephrectomy in the kidney donors was significantly greater than the enzyme excretion per single kidney in the control group (p less than 0.001). No correlation was found between the degree of enzymuria and either glomerular filtration rate or time since nephrectomy. The elevated activity of urinary enzymes in kidney donors may be related to increased metabolism by the renal tubular cells after contralateral nephrectomy. This study suggests that long-term compensatory hyperfiltration does not damage tubular cells, at least over this time scale.

Quality control material for activity determinations of urinary enzymes

We examined the stability of N-acetyl-beta-D-glucosaminidase (EC 3.2.1.30), alanine aminopeptidase (EC 3.4.11.2), alkaline phosphatase (EC 3.1.3.1), gamma-glutamyltransferase (EC 2.3.2.2), and lysozyme (EC 3.2.1.17) in urine prepared by gel filtration and supplemented with albumin, or ethylene glycol, or ethylene glycol plus albumin during storage at -20 degrees C for a period of 12 months. The stability was assessed by linear regression analysis of monthly values versus time. All enzymes except for gamma-glutamyltransferase could be considered stable for about one year in all three control materials provided that maximum change of 10% of the starting enzyme activity is accepted as tolerable. If ethylene glycol is used as stabilizer, its suitability must be tested and its inhibitory effect on enzyme activities must be taken into account in intermethod comparisons, because in some methods, it may be removed in a pretreatment step.

Contrast agent nephrotoxicity: comparison of ionic and nonionic contrast agents

The effects on glomerular and proximal tubular function of an ionic contrast agent (sodium meglumine diatrizoate) and a nonionic agent (iopamidol) were compared in 34 patients with normal renal function. The patients received large doses (2.5 ml/kg body weight) of contrast material for IV digital subtraction angiography. Urine samples, collected before, immediately after, and on the first and third days after digital subtraction angiography, were analyzed for albumin, alanil-aminopeptidase, alpha-glucosidase, and beta-2-microglobulin. The changes noted were mild and of short duration with both contrast agents, despite the high dose given. These results suggest that, at least as far as renal toxicity is measured by these tests is concerned, ionic monomers can be safely used instead of more expensive nonionic media in procedures, such as digital subtraction angiography, that require high doses of contrast material.

Diagnostic significance of different urinary enzymes in patients suffering from chronic renal diseases

The urinary enzymes alanine aminopeptidase (EC 3.4.11.2), alkaline phosphatase (EC 3.1.3.1), gamma-glutamyltransferase (EC 2.3.2.2), N-acetyl-beta-D-glucosaminidase (EC 3.2.1.30), and ribonuclease (EC 3.1.4.22) were measured in 66 healthy persons and 52 patients suffering from chronic renal diseases (pyelonephritis, glomerulonephritis). The residual renal function of patients characterized by 99mTc-diethylenetriaminopentaacetate isotope clearance was only moderately reduced. Except for gamma-glutamyltransferase, patients generally showed increased urinary enzyme excretions. N-Acetyl-beta-D-glucosaminidase was more sensitive to detect renal dysfunction than the other enzymes and the conventional parameters serum creatinine, total protein excretion, and the measurement of glomerular filtration rate. The determination of this enzyme can be recommended as a suitable diagnostic parameter in nephrology.

Increased tubular enzyme excretion in preeclampsia

The pathophysiology of preeclampsia includes ischemia and microinfarctions of the kidney, which could induce renal tubular cells to release enzymes into urine. We therefore measured the concentrations of two markers of renal tubular damage, N-acetyl-beta-D-glucosaminidase and alanine aminopeptidase, in urine specimens from women with mild or severe preeclampsia and compared the results with those from healthy pregnant and nonpregnant women. The median urinary concentrations of N-acetyl-beta-D-glucosaminidase and alanine aminopeptidase in women without preeclampsia increased progressively through the first, second, and third trimesters and reached maximum values of 1.12 and 0.77 U/mmol creatinine, respectively. Median concentrations of the two enzymes were significantly higher in women with mild preeclampsia (N-acetyl-beta-D-glucosaminidase = 1.40, alanine aminopeptidase = 1.12 U/mmol creatinine) or severe preeclampsia (N-acetyl-beta-D-glucosaminidase = 2.90, alanine aminopeptidase = 1.26 U/mmol creatinine). This increased enzyme excretion indicates subclinical preeclamptic renal tubular damage.

Urinary enzyme activities in patients treated with gold and other antirheumatic drugs

We have studied 48 rheumatoid arthritis (RA) patients treated with nonsteroidal antiinflammatory drugs (NSAIDs), except salicylates, in 31 of whom parenteral gold was associated as therapeutic agent. In order to assess initial tubular involvement, the activities of some urinary enzymes were measured: N-acetylglucosaminidase (NAG, EC 3.2.1.30), microsomal amino-peptidase (MAP, EC 3.4.11.2) and gamma-glutamyltransferase (GGT; EC 2.3.2.2). Results were compared with a control group of 51 subjects of similar age, with no rheumatic symptoms and normal renal function. Both groups of patients (31 with gold therapy and 17 without) showed a significantly increased activity of NAG in urine, but the increase was greater in those treated with gold. MAP and GGT were not elevated significantly in either group. There was no correlation, however, between the increase of NAG and the cumulative dose of gold. NAG, MAP and GGT activities in serum yielded no relevant information. All the usual tests of renal function were also normal. Determination of NAG in urine may be regarded as a sensitive test, capable of detecting selective involvement of renal tubular cells, whose final diagnostic and prognostic significance merits further evaluation.

Alanine aminopeptidase and beta 2-microglobulin excretion in patients receiving vancomycin and gentamicin

The effects of vancomycin, gentamicin, and combination vancomycin-gentamicin treatments on alanine aminopeptidase (AAP) and beta 2-microglobulin (beta 2M) elimination in 30 hospitalized patients were assessed and compared with elimination in a control group. Twenty-four-hour urine excretion values for AAP and beta 2M were determined on treatment day 1 and day 5 for patients receiving the three treatment regimens and for the control group. AAP excretion values for the vancomycin-treated group were not found to be statistically different from those of the control group. Both the gentamicin and the vancomycin-gentamicin groups had statistically higher AAP excretion values on treatment day 1 as well as on treatment day 5 when compared with the vancomycin and control groups. AAP excretion on day 5 of treatment was highest for the vancomycin-gentamicin group. Overall, beta 2M elimination was variable in all treatment groups. Although the beta 2M values were elevated as early as day 1 in all treatment groups, they were significantly elevated only in the vancomycin-gentamicin group on day 1 and only in the gentamicin group on day 5 compared with the vancomycin and the control groups. AAP appears to be a sensitive indicator of renal tubular damage. The combination of vancomycin and gentamicin results in greater AAP excretion than does either agent alone.

Variation of urinary enzymes N-acetyl-beta-glucosaminidase, alanine-aminopeptidase, and lysozyme in patients receiving radio-contrast agents

A urinary enzyme pattern consisting of two lysosomal enzymes, N-acetyl-beta-glucosaminidase and lysozyme, and one enzyme originating from kidney tubular brush border membrane, alanine-aminopeptidase, were studied in 30 patients undergoing intravenous urography and arteriography. N-acetyl-beta-glucosaminidase and lysozyme showed the greatest diagnostic sensitivity and were still abnormal on the fifth day after the administration of radio contrast agent. The results, which are statistically significant (Student's t test), suggest that radio-contrast agents are potentially nephotoxic.