Contrasting effects of gentamicin and mercuric chloride on urinary excretion of enzymes and phospholipids in the rat

Gentamicin induces a phospholipiduria in the rat. We sought to determine whether the phospholipiduria reflected shedding of brush border membrane by measuring the urinary excretion of membrane marker enzymes, by defining the composition of the urinary phospholipids, and by examining the renal cortex and urinary sediment using transmission electron microscopy of rats injected with gentamicin sulfate (100 mg/kg of body weight for 1 to 6 days). The results were compared and contrasted with those of rats injected with mercuric chloride, a nephrotoxin known to cause selective injury to the brush border membrane. Gentamicin-injected rats exhibited a phospholipiduria that by the third day was 10-fold above the baseline level. In contrast the brush border membrane enzymes alanine aminopeptidase and gamma-glutamyl transferase and the lysosomal enzyme N-acetyl-beta-glucosaminidase increased less than 1-fold above baseline. Electron microscopy of the renal cortex revealed the presence of myeloid bodies within lysosomes of proximal tubule cells and lying free within the lumen. The brush border membrane was largely intact. The urine sediment was dominated by the presence of myeloid bodies; there was little evidence of brush border membrane fragments. The urinary phospholpids were enriched in phosphatidylinositiol, phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine. This pattern is similar to that of a lysosomal fraction enriched in myeloid bodies. Rats injected with mercuric chloride exhibited a phospholipiduria associated with sharp increases (7- to 15-fold) in the urinary excretion of brush border membrane enzymes, whereas N-acetyl-beta-glucosaminidase increased less than 3-fold. Electron microscopy revealed blebbing of the apical membrane with loss of microvilli of proximal tubular cells particularly evident along the pars recta. The urinary sediment contained microvilli and fragments of plasma membrane but no myeloid bodies. The urine contained large quantities of sphingomyelin. In the rat renal cortex the brush border membrane is the major source of this phospholipid. We conclude that the phospholipiduria induced by mercuric chloride is derived primarily from the shedding of brush border membrane fragments into the urine. In contrast, the urinary excretion of phospholipid induced by gentamicin reflects primarily the extrusion of the lysosomal myeloid body from proximal tubular cells. We speculate that the origin of the phospholipids making up the lysosomal myeloid body may be the endocytic vesicle that mediates the transport of aminoglycosides into the lysosomal system.

Early biochemical effects of an organic mercury fungicide on infants: "dose makes the poison"

Phenylmercury absorbed through the skin from contaminated diapers affected urinary excretion in infants in Buenos Aires. The effects were reversible and quantitatively related to the concentration of urinary mercury. Excretion of gamma-glutamyl transpeptidase, an enzyme in the brush borders of renal tubular cells, increased in a dose-dependent manner when mercury excretion exceeded a "threshold" value. Urine volume also increased but at a higher threshold with respect to mercury. The results support the threshold concept of the systemic toxicity of metals. gamma-Glutamyl transpeptidase is a useful and sensitive marker for preclinical effects of toxic metals.

[Tubular dysfunction in renal lithiasis: cause or consequence?]

To investigate whether overall tubular dysfunction is encountered in a particular subgroup of patients with urolithiasis, the following parameters of renal tubular function have been measured in fasting morning urine in 124 male stone formers: excretion of lysozyme and gamma-glutamyl transpeptidase (gamma-GT), fractional excretion (FE) or glucose, insulin, bicarbonate after an alkali load, and theoretical phosphate threshold (TmP/GFR). The following have been diagnosed: primary hyperparathyroidism (n = 3), medullary sponge kidneys (n = 5), hyperuricemia (n = 8), cystinuria (n = 1), struvite nephrolithiasis (n = 2), idiopathic hypercalciuria of the absorptive (n = 16), dietary (n = 46) or renal (n = 5) type, and normocalciuric idiopathic urolithiasis (n = 38). Urinary excretion of lysozyme and of gamma-GT were elevated in 14% and 21% of patients respectively; FE glucose and FE insulin were elevated in 6% and 8% of patients respectively. In 62% of the patients TmP/GFR was below 0.95 mmol/l and in 52% of the patients FE HCO3 after alkali load was above normal. The findings show that a large number of stone formers have signs of renal tubular dysfunction; apparent renal leaks of phosphate and of bicarbonate are the most frequently encountered defects; while they are not specific for a given etiologic group of patients, they have been found in each group. The latter observation suggests that nephrolithiasis itself can damage renal tubular function.

Evaluation of a technique for measurement of gamma-glutamyltranspeptidase in equine urine

gamma-Glutamyltranspeptidase (GGT) activity in equine urine was measured, using an assay developed for use with serum and was found to be reproducible. The GGT activity was measured in samples prepared by serial dilution of exogenous GGT with equine urine, and the activity was determined to be linear between 21 IU/L and 407 IU/L. The behavior of exogenously added GGT was compared in equine serum and urine. The enzyme behaved similarly in both fluids. The GGT activity was measured in serum and urine samples after storage at -20, 4, and 25 C for 24 and/or 72 hours. Enzyme activity decreased after storage at all temperatures and times, but the decrease was greatest and most variable at -20 C. The urine GGT: urine creatinine ratio was calculated on serial urine samples collected over 24 hours. Although the urine GGT activity and creatinine concentration had significant variation, the ratio remained constant. The urine GGT: urine creatinine ratio was calculated from random urine samples collected from 27 clinically healthy adult horses and was found to be 10.52 +/- 4.78 (mean +/- SD).

Reference ranges and methodological aspects in the urinary measuring of lysozyme, malate-dehydrogenase, gamma-glutamyltransferase and alpha-glucosidase

The urinary excretions of lysozyme (LYS), malate-dehydrogenase (MAD), gamma-glutamyltransferase (GGT) and alpha-glucosidase (AGL) were measured in a group of normal subjects in basic conditions, during forced diuresis, at different hours of the day and with urinary collection periods of different lengths. The results have been expressed in the principal ways used in clinical practice. The best way to express the excretions of GGT and AGL was with the fractional excretions. For LYS and MAD, the fractional clearances appeared to be theoretically valuable. They were not significantly influenced by sex or by the different urinary collections. Forced diuresis caused a significant scattering of enzymuria.

Detection of renal tubular lesions after abdominal aortography and selective renal arteriography by quantitative measurements of brush-border enzymes in the urine

Quantitative determination of brush-border enzyme excretion in the 24-hour urine is a much more sensitive index of renal tubular damage after aortography and selective renal arteriography than the conventional renal function tests such as serum creatinine and clearance determinations. Among the five brush-border enzymes which we investigated, alkaline phosphatase (AP) was the most sensitive diagnostic pointer. In 90% of hypertensive patients without detectable pre-existing renal parenchymal damage, abnormal levels of AP excretion in the urine were found on the same day as or on the day after the intra-arterial injection of contrast medium. Measurement of other brush-border enzymes does not provide any further diagnostic information. Provided there is no pre-existing renal parenchymal damage, the lesion caused by the contrast medium is transient and is usually reversed within 48 h. For the early detection of tubular lesions caused by tri-iodinated benzoic acid derivatives, AP excretion in the 24-hour urine should be measured at least twice--on the day of the contrast medium injection and on the following day.

Are urinary enzymes useful markers of kidney damage in obstructive jaundice? An experimental study on Sprague-Dawley rats

To evaluate the reliability of urinary enzymes as markers of renal tubular damage in obstructive jaundice, research was carried out on 26 Sprague-Dawley rats submitted to bile duct ligation and on 16 sham-operated rats. The fractional clearances of lysozyme (CfrLYS) and of malto-dehydrogenase (CfrMDH)-indices of tubular function-and the fractional excretions of gamma-glutamyltransferase (UfrGGT) and of alpha-glucosidase (UfrAGL)-indices of tubular anatomic damage - were measured 5, 10, 20 and 30 days after operation. Creatinine clearance, urinary sodium excretion, urinary potassium excretion, proteinuria, plasma bilirubin and bile acids were also measured. Kidneys were taken for histology. All rats submitted to common bile duct ligation had high levels of bilirubin and bile acids; proximal tubules were damaged and the extent of the lesions increased with time. However, creatinine clearance, urinary sodium excretion, proteinuria, CfrMDH and UfrAGL gave no indication of renal lesions, whereas CfrLYS and UfrGGT were significantly higher 20 and 30 days after bile duct ligation, respectively. These findings show that CfrLYS and UfrGGT could be useful tests for renal tubular lesions in jaundice.

Sensitivity of urinary enzymes as indicators of renal toxicity of the anticancer drug cis-platin

Rats were intravenously injected with cis-platin in order to evaluate the sensitivity of noninvasive means of detecting renal toxicity. Doses of 8 mg/kg and 2 mg/kg were used and 7 urinary parameters (osmolality, glucose, protein, and 4 enzymes) were compared with blood urea nitrogen (BUN) and histology. Urinary enzymes usually were elevated by Day 2 posttreatment and in two cases by Day 1. Protein and glucose were elevated by Day 3 and demonstrated a greater quantitative change (10-12X control) than did urinary enzymes (2-3X controls). Enzymes, protein, and glucose all returned to control levels by Day 7 or 8, and most parameters were re-elevated again by Day 10 or 12. BUN was unaltered at the lowest dose and was increased to three times control by Day 3 after the highest dose. Cis-platin induced a mild nephrosis at the lowest dose and a proximal tubular necrosis at the highest dose. The lesion occurred at the corticomedullary junction. Biochemical changes did not correspond to the times of greatest morphological changes. Large day-day and animal-animal variation made selection of a most sensitive parameter difficult. It is concluded that one parameter is insufficient to define early renal toxicity and that a battery of several parameters would provide a better evaluation of the onset of renal toxicity.

Comparative investigations on the effects of acute intraperitoneal cadmium, chromium, and mercury exposure on the kidney

Urinary excretion of lactate dehydrogenase (LDH), glutathione-S-transferase (GST), leucine arylamidase (LAS), gamma-glutamyltransferase (GGT), beta-galactosidase (GAL), beta-N-acetyl-D-glucosaminidase (NAG), sodium, and glucose were determined in female Sprague-Dawley rats the subsequent three days after intraperitoneal treatment with single doses of 4.5 mg CdCl2 X 1H2O/kg, 20 mg Na2CrO4/kg, and 0.75 mg HgCl2/kg body weight. Although the pathological effects were localized within the same part of the nephron (i.e., the proximal tubule), there were marked differences with regard to the extent and time course of the parameters affected. Treatment with cadmium resulted essentially in a marked decline in sodium and glucose excretion. The administration of chromate led to a slightly to moderately elevated excretion of the enzyme activities measured with the cytosolic LDH as the most increased enzyme (ca. 500% of controls on Day 3 postadministration). Median glucose excretion was unaffected whereas sodium excretion was transiently reduced. The maximum of enzyme excretion after HgCl2 was essentially the same on the first day postadministration and the amount of enzyme activity in urine up to 20 times higher compared to that after chromium. Sodium excretion was below that of controls on Days 2 and 3, whereas glucose excretion was markedly elevated (up to 8000% of controls). The results indicate that it is possible to discriminate with the use of selected urinary enzymes, substrates, and electrolytes various kinds of nephrotoxic actions not only in different but also within the same part of the nephron.

Urinary enzyme excretion in acute and subacute experimental lithium administration

Blood lithium (Li) levels, renal functional parameters and urine excretion of enzymatic activities having different intracellular sites were investigated on rats submitted to acute and subacute Li chloride administration. In acute experiments increased levels of all detected enzymes were assayed following Li single doses of 5 and 10 mEq/kg b.w. In subacute poisoning, urine output of lactate dehydrogenase, aspartate transaminase and alanine transaminase was significantly over the basal ranges following 15 days in concomitance with marked elevation of plasma Li levels and exhibited progressive increase until 30 days; on the 10th day following Li withdrawal, elevated excretion of enzymatic activities was still assayed. The results are in agreement with data about the localization of the histologic lesions involving different sites of the nephron in acute Li poisoning and the distal tubular tract in subacute toxicity. In subacute administration the output of cytoplasmic and mitochondrial activities can be assumed as an index of damage of the nephron cells which can persist following Li withdrawal. Our findings indicate that the urine enzyme assay is a valuable tool to detect renal damage in experimental Li nephropathy.

Exercise-induced urinary abnormalities in long-distance runners

The post-exercise urine samples from 122 long-distance runners showed evident abnormalities upon microscopic examination in 95% of all subjects. Proteinuria, alone or with microscopic hematuria, was frequently found. Macroscopic hematuria was a rare occurrence. The urine samples collected in 30 runners before, immediately after the race, and 6, 12, 24, 36, and 48 h later showed a significant post-race decrease in the osmolarity and a significant increase in gamma-glutamyl transferase and N-acetyl-beta-glucosaminidase enzyme activity. Plasma renin activity and plasma aldosterone, determined before and after the race in nine runners, showed a significant increase in the post-race samples. The abnormal urinary findings disappeared in all cases within 24-36 h. It can be concluded that urinary abnormalities are very common after exercise. These abnormalities are most often of a "renal" origin, probably due to a temporary hemodynamic impairment, partially of glomerular but principally of tubular function.

Multiple forms of alanine aminopeptidase, alkaline phosphatase and gamma-glutamyltransferase in urine of healthy persons, patients suffering from kidney diseases and patients with kidney transplants

The catalytic activities of alanine aminopeptidase, alkaline phosphatase and gamma-glutamyltransferase were determined in the soluble and particulate fractions of urine, after ultracentrifugation. In healthy adults the fractional catalytic activities in the supernatants were 0.53, 0.56 and 0.24, respectively. Nearly the same proportions were found in children. In patients suffering from chronic kidney diseases there was a tendency for the proportion of catalytic activity in the soluble fraction to increase. However, the separation into the multiple forms gave no higher diagnostic reliability than the determination of total catalytic activity of the respective enzymes. The determination of multiple forms has no clinical significance in the detection of rejection episodes in renal transplant recipients.

[Urinary enzyme excretion in cephalothin therapy in adults and children]

A damage of the kidney, particularly of proximal tubular cells, can be indicated by an increased concentration of definite enzymes in urine. After gynecological operation the repeated application of 8 g cephalothin daily provokes an higher increase of enzyme concentrations in urine than the application of ampicillin under the same conditions. These results show that cephalothin produces a slight alteration of tubular cells, probably without practical importance. In contrast to this, in children a total dose of 1.5 up to 6 g cephalothin, administered after an operative correction of vesikoureterale reflux, provokes no marked changes in urinary enzyme excretion. Probably, in these children the determination of urinary enzyme excretion is not a suitable parameter to demonstrate a slight tubulotoxic damage.

Electrophoretic variants of alanine aminopeptidase, alkaline phosphatase, and gamma-glutamyltransferase in urine

The three brush-border enzymes--alanine aminopeptidase (EC 3.4.11.2), alkaline phosphatase (EC 3.1.3.1), and gamma-glutamyltransferase (EC 2.3.2.2)--are present in the urine of healthy persons in two variants, a particulate form and a soluble one. They can be separated by electrophoresis in agarose gel and by ultracentrifugation. The particulate forms exhibit similar electrophoretic mobility, but the soluble forms of these brush-border enzymes differ in their electrophoretic mobilities. The enzyme components of the particulate activity can be mobilized by Triton X-100 and trypsin. The electrophoretic mobility of the soluble forms of alanine aminopeptidase and gamma-glutamyltransferase is slowed by neuraminidase treatment. Both forms of gamma-glutamyltransferase are influenced in their electrophoretic mobility by treatment with n-butanol/diisopropyl ether, showing their lipid dependence. These findings enhance our knowledge of the biochemical nature of brush-border enzymes in urine.

Changes in enzyme activities in the urine and tissues of rats fed sodium o-phenylphenate

The activities of certain enzymes in the urine and tissues of rats given 2% sodium o- phenylphenate in the diet for 20 wk were examined. Urinary gamma-glutamyl transpeptidase (gamma GTP) decreased immediately after the start of feeding of the treated diet and its activity remained low for 20 wk. The gamma GTP and alkaline phosphatase (ALP) activities in kidney homogenate decreased to about 80% of the control at 20 wk, but G6PD activity was significantly increased; Na,K-ATPase was unchanged. On the other hand, the gamma GTP activity in the liver homogenate of treated rats was increased to about eight times that of the controls, the G6PD activity showed a significant increase, but the ALP and Na, K-ATPase activities were not significantly different from the control values. The glutathione concentration in the livers of treated rats was significantly reduced.

Effect of subtotal nephrectomy on the excretion of urinary alanine aminopeptidase and gamma glutamyltransferase in the male Wistar rat. A long-term study

The study of alanine aminopeptidase (AAP) and gamma glutamyltransferase (GGT), two integral components of the brush border membrane of the proximal kidney tubule, has generated considerable interest for research on the nephrotoxicity of drugs. AAP and GGT activity in urine correlate strongly. The three phases after a subtotal nephrectomy can be described as follows: the first phase, lasting 1 month, is characterized by an abrupt decrease of 70% in AAP and GGT activity, corresponding to the excised kidney mass. During the second phase, a partial recovery occurs representing nearly 50% of the AAP and GGT activity in the control group (30th to the 75th day after nephrectomy). These activities begin to decrease slightly in the third phase until the end of the experiment. In terms of remaining kidney mass, the results demonstrate a twofold increase of the AAP and GGT activity. The same phenomenon can be seen in the excretion of creatinine, except that the compensatory activity is multiplied by four in the remaining kidney. Good correlations between AAP activity, GGT activity, urinary creatinine, 24-hour urine volume, and 24-hour creatinine output are found in both experimental and control groups.

[Nephrotoxicity of contrast media. Comparison of iopamidol and diatrizoate by measurement of urinary enzymes after urography]

An ionic (diatrizoate) and a non ionic (iopamidole) radiocontrast medium were compared as to their nephrotoxicity in a cohort of 21 patients with renal disease, 18 of which with normal renal function. The elevation of the urinary excretion of enzymes from renal tubular cells has been considered as a good index for renal tubular damage. We measured two lysosomal enzymes (NAG and beta glucuronidase) and a brush-border enzyme (gamma GT). In all patients we demonstrated an elevation of urinary excretion of the three enzymes already 12 hours after contrast medium administration. However, the elevation was statistically significant only after employment of the ionic contrast medium and concerned gamma GT and beta-glucuronidase; the urinary excretion of NAG did not vary significantly. Urinary enzymes levels returned to basal values 36 hours after intravenous pyelography. In conclusion, iopamidole showed a lower nephrotoxicity with respect to diatrizoate, as demonstrated by the lower levels of urinary enzymes excretion reached after its use.

Functional and morphological changes in the rat kidney after long-term adrenaline application

A 24 h lasting long term adrenaline application in the form of subcutaneously implanted retard-tablets causes functional and morphological changes in the kidney, which are dose dependent and either reversible or irreversible. Animals in the V 15 group received one 15 mg and in the V 30 group two 15 mg adrenaline tablets resp. The tablets were removed after 24 h and a clearance depot capsule was implanted in the abdominal cavity. The test period extended from 22 h after removal of the retard tabl. to 21 d thereafter. Inulin (except the V 30 grp.), PAH and urea clearance are showing no significant differences. The data of urine gamma-GT activity, urea and urea-N in serum and urine, S-glucose, S-triglycerides, Combur-8-test, Na+ and K+ levels are in normal ranges. Morphological changes were found in the glomerula and tubular regions. Both the number of damaged nephrons and the extent of the damage depend upon the doses of adrenaline given. All glomerula with visible serious changes are irreversibly damaged; this was not true in case of the tubule. In the latter, after 7 d, the fatty deposits had diminished or disappeared.