Renal function tests: what do they mean? A review of renal anatomy, biochemistry, and physiology

The effect of epigallocatechin-3-gallate on the renal dysfunction in the obstructed kidney in the rat

INTRODUCTION

Epigallocatechin-3-gallate (EGCG) is the most active catechin polyphenol extracted from the green tea. EGCG has protective effects in various renal and non-renal conditions. The aim of this study was to investigate the effect of EGCG on the alterations in renal functional parameters following reversible unilateral ureteral obstruction (UUO) in the rat.

METHODS

Wistar rats underwent reversible left UUO for 72 hours. Group-EGCG (n=10) received intraperitoneal 50 mg/kg/day of EGCG whereas Group-Vx (n=10) had only normal saline. Five days post UUO reversal, renal functions of both kidneys were measured using clearance techniques and the gene expression of some of kidney injury markers (KIM-1 and NGL) and the pro-inflammatory mediator (TNF-α) were determined using real time PCR.

RESULTS

Renal blood flow, glomerular filtration rate, urine volume and urinary sodium excretion were still altered 5 days post-UUO reversal. Fractional sodium excretion had returned to baseline values by that time. EGCG did not significantly affect any of the renal functional parameters of the obstructed kidney (P>0.05 for all). However, it significantly decreased the gene expressions of KIM-1, NGAL and TNF-α in the left obstructed kidney in Group-EGCG compared to Group-Vx (28±27 vs. 286±107, 1.1±0.2 vs. 10.9±4.3, and 0.8±0.1 vs. 1.5±0.2, P<0.05 for all).

CONCLUSION

EGCG appears to have no significant protective effect on the haemodynamic or tubular glomerular functions when measured as early as five days post reversal of UUO despite the attenuation of some of the kidney injury markers and pro-inflammatory mediators.

Effect of the lipid peroxide reaction caused by repeated cold stress on cisplatin-induced nephrotoxicity

The peroxide reaction in mouse kidney was examined in order to determine the relationship between the lipid peroxide reaction caused by SART (specific alternation of rhythm in temperature) stress and that caused by drug administration. After exerting SART stress for one wk on 6-wk-old male ddY mice (stress group), the peroxide reaction generated by the administration of a single dose of cis-diamminedichloroplatinum (cisplatin: CDDP, 10 mg/kg, i.p.) into SART-stressed mice (stress + CDDP group) was compared with the reaction of CDDP-administered nonstressed mice (CDDP group), saline-administered nonstressed mice (saline group), and saline-administered SART-stressed mice (stress + saline group). Lipid peroxidation in the kidneys was significantly higher in the stress group upon cessation of stress exertion than in the normal group. However, no significant difference in the lipid peroxide level after administration of CDDP was observed between the CDDP groups. The renal glutathione levels were significantly different between the CDDP groups and the saline administered groups. These results indicate that the peroxide reaction is generated in the kidneys by stress, but stress has no effect on the peroxide damage caused by CDDP administration. However, the contribution of stress to renal function impairment requires further evaluation.

The nephrotoxicity, cytotoxicity and renal handling of a cisplatin-methionine complex in male Wistar rats

When cisplatin is administered in the form of a cisplatin-methionine substitution complex, high doses of cisplatin can be tolerated with no obvious signs of renal toxicity. We have demonstrated that male Wistar rats receiving a single i.p. dose of cisplatin-methionine at a 1:5 ratio (by weight) did not exhibit cisplatin-induced nephrotoxicity, while cisplatin administered alone at an identical concentration (6 mg/kg) resulted in marked renal toxicity in all animals treated. Using renal cortical slices prepared from untreated rats, we demonstrated that cisplatin, but not cisplatin-methionine, inhibited the accumulation of 14C-tetraethylammonium (TEA). This observation suggests that cisplatin, unlike cisplatin-methionine, is a substrate for the organic base transport system. In addition, cisplatin alone was more cytotoxic to C6 glioma cells in vitro than the cisplatin-methionine complex. Exposure of C6 glioma cells to cisplatin-methionine, however, resulted in a 50%-60% reduction in 3H-thymidine incorporation at cisplatin:methionine ratios up to 1:10. These results indicate that cisplatin-methionine is significantly cytotoxic yet lacks cisplatin-associated renal toxicity and may, therefore, have a role in the treatment of human malignancies.

Assessment of renal function and damage in animal species. A review of the current approach of the academic, governmental and industrial institutions represented by the Animal Clinical Chemistry Association

There are a wide variety of laboratory tests available to assess damage to and functional impairment of the kidneys, although the effectiveness of these tests varies greatly depending upon the site specificity of the damage and to a lesser extent upon the animal species involved. Several traditional tests of renal dysfunction and damage, including plasma creatinine and urea, and urinalysis (dipstick and/or quantitative protein), can be used in the first instance to detect nephrotoxicity. A second tier of specific, targetted indicators (concentration test, urinary enzymes, clearance of analytes, specific proteins, etc.) may then be applied to identify further the site of the lesion and the functional status of the kidneys. The glomerular filtration rate (GFR) may be estimated from the clearance of exogenous and endogenous substances. The difficulty in obtaining accurately timed urine samples limits the value of these tests in small animals, although methods that do not involve urine collection are available. The kidney is the origin of several enzymes found in urine that can be used to monitor the toxic effects of chemicals and therapeutic substances. Selective measurement of enzyme activities in urine can be used to detect the site of the renal lesion after traditional tests have established the presence of renal injury. Separation of proteins in urine by electrophoretic techniques may also be used to discriminate damage to different parts of the nephron. Renal cell excretion in urine is a sensitive but unreliable indicator of acute damage to the proximal tubule. The rate of cell excretion is not a good predictor of the severity of tubular injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Toxicity-distribution relationships among 3-alkylfurans in mouse liver and kidney

The present study was designed to extend previous observations regarding toxicity of furans and related compounds to liver and kidney. It was desired to test a series of homologous 3- alkylfurans , where changes in lipophilic character might be related to changes in toxicity. Additionally, it was desired to measure distribution of toxins to the target organs to ascertain whether organ selectivity might be determined by the concentrations attained in the target organs by the toxins. A synthesis for 3- ethylfuran and 3- pentylfuran was devised, and the toxicity of these, in addition to 3- methylfuran and furan itself, to mouse liver and kidney at 2.6 mmol/kg was determined. 2- Furamide and 2- ethylfuran were used as examples of substances known to be toxic to liver and kidney, respectively. 3- Methylthiophene was also included to determine whether results with furans extend to the closely related thiophenes . Histopathological examination of both organs was done, and quantitative estimates of liver toxicity were obtained from plasma levels of glutamate-pyruvate transaminase. Renal urine concentrating ability and plasma urea nitrogen levels were useful as quantitative indices of nephrotoxicity. It was found that both 3-ethyl and 3- pentylfuran exhibited pronounced toxicity to the kidney, and that both also caused moderate liver damage. Furan caused serious damage to the liver and produced somewhat lesser effects on the kidney. Equimolar doses of 3- methylfuran did not significantly damage either organ. Among the 3-alkyl furans, there is an impression that the more volatile compounds damage lung (3- methylfuran is reported to be a potent lung toxin), with liver and kidney toxicity increasing with molecular weight, and that compounds found in higher concentration produce greater damage in liver and kidney. However, among compounds other than alkyl furans, there is no obvious correlation between toxicity and organ concentration of toxin.

Effects of diisopropylfluorophosphate (DFP) on renal function in the rat

Numerous studies have suggested a role for the nervous system in renal function. Several cholinergic agents have been examined for effects in vivo and in renal slices. Effects mediated through the vascular system and also direct effects have been reported. In this study an irreversible cholinesterase inhibitor, diisopropylfluorophosphate (DFP) in doses of 1-4 mg/kg, was tested on renal function. A single dose of DFP (2, 3 or 4 mg/kg) caused an increased flow of urine of low osmolality over the 6 h after the administration of the drug with essentially a return to control status by 24 h after either of the lower doses. Twenty-four hours after 4 mg/kg, urine volume was less and urine osmolality greater than control. Renal and brain cholinesterases remained depressed 24 h after DFP. In acute experiments on anesthetized animals, inulin clearance was increased by the lower doses and decreased by the highest dose of DFP. Renal blood flow measured with an electromagnetic flow meter showed a similar dose-response relationship. However, urine flow increased at all doses. The increased urine flow associated with decreased inulin clearance (4 mg/kg) and renal blood flow (3 or 4 mg/kg) suggest a direct effect of DFP on renal tubular function. These effects do not appear to be related to inhibition of cholinesterase.

Onset of and recovery from acute N-(3,5-dichlorophenyl)succinimide-induced nephrotoxicity in Sprague-Dawley rats

The time course for the onset of N-(3,5-dichlorophenyl)succinimide (NDPS)-induced nephrotoxicity was studied in male Sprague-Dawley rats. The ability of rats to recover from a single nephrotoxic dose (100 or 200 mg/kg) of NDPS also was examined. One hour following NDPS administration (200 mg/kg, i.p.), p-aminohippurate (PAH) accumulation by renal cortical slices was decreased 51%. Changes in renal morphology, proteinuria, hematuria, and diuresis were observed at 3 h. Renal damage at 6 h was similar to that seen at 24 h with tubular necrosis greater than that observed at 3 h and some lumina plugged with PAS+ material. Accumulation of both PAH and tetraethylammonium (TEA) by renal cortical slices was decreased; and proteinuria, hematuria, and polyuria were increased at 6 h and 24 h. Blood urea nitrogen (BUN) was not increased until 24 h. Renal function began to return to normal in rats receiving NDPS (100 mg/kg, i.p.) by 48 h, and functional recovery was complete by 168 h, although slight morphological changes were still evident. However, not all rats receiving NDPS (200 mg/kg, i.p.) recovered by 168 h, and some rats (3 of 7) died of renal failure between 96 h and 168 h. Widespread tubular necrosis and increased kidney weight were also present in this group at 168 h. Thus, NDPS-induced nephrotoxicity was evident by 1 h, established by 6 h and maximum between 24 h and 48 h. Recovery from NDPS-induced nephropathy was found to be dose-dependent, and incomplete in some animals at a dose of 200 mg/kg.

Assessment of functional, morphological, and enzymatic tests for acute nephrotoxicity induced by mercuric chloride

The relative merits of a comprehensive series of contemporary methods for detection of acute nephrotoxicity were evaluated. Male Sprague-Dawley rats were given 0, 0.25, 0.5, 1.0, or 3.0 mg mercuric chloride (HgCl2)/kg body weight by ip injection. Indices of nephrotoxicity were examined 8, 24, 48, 72, and 96 h later. Alterations in urine osmolality, volume, and protein levels were seen within 24 h in response to 1 mg/kg or more of HgCl2. Administration of 0.5-3.0 mg/kg produced dose-dependent increases in urinary excretion of maltase activity and glucose by 24 h, the period of peak effect. There was no increase in maltase or alkaline phosphatase (AP) activity in the serum of these animals. Enzymuria was not apparent in rats that had marked elevations in serum AP, argininosuccinate lyase, and ornithine carbamyl transferase activities as a result of physical (i.e., dichlorodifluoromethane-frozen) or chemical (carbon tetrachloride-induced) damage of the liver. Morphological alterations, in the proximal tubular epithelium of perfusion-fixed kidneys from HgCl2-dosed rats, paralleled the changes in enzyme excretion with respect to time of onset and dose-effect. There was a dose-dependent inhibition of tetraethylammonium (TEA) and p-aminohippurate (PAH) uptake by renal cortical slices at 24 h. Interestingly, increases in uptake of TEA and PAH were seen 8 h after a 1-mg/kg dose. Clearance of inulin and PAH in vivo were altered at 8 h by 0.5 and 1 mg/kg. Marked depression of these functional indices was seen at 24 h, by which time blood urea nitrogen (BUN) levels were increased. The 0.5- and 1.0-mg/kg doses also produced time- and dose-dependent increases in intracellular Na+ content which were maximal at 24 h. These results illustrate the importance of using a combination of biochemical and functional tests to elucidate the sequence of events in the kidney following toxic insult. Nevertheless, some of the simpler, traditional techniques (e.g., histopathology, urinalyses, BUN) were sensitive and organ-specific, and should continue to be very useful in nephrotoxicity testing/screening.

Effect of halogenated vinyl cysteine conjugates on renal tubular active transport

Addition of halogenated vinyl cysteine conjugates to isolated rabbit kidney tubule suspensions resulted in a decrease in the active transport of para-aminohippuric acid (PAH) and tetraethylammonium bromide (TEA). At 10(-5) M vinyl cysteine conjugate, tubule to medium accumulation ratios (T/M) were similar to those of controls while at 10(-3) M the T/M values decreased to 1, indicating complete inhibition of active accumulation of PAH or TEA. The decreased active transport was not caused by inhibition of mitochondrial oxidation since incubations in the presence of 10(-3) M halogenated vinyl cysteine did not inhibit tubule O2 utilization or production of 14CO2 from [14C]glucose or [14C]succinate. A mechanism is proposed whereby toxicity may result from covalent binding of an active intermediate, produced by enzyme cleavage, to membrane associated nucleophilic groups thereby decreasing active transport.

Correlation of the in vivo and in vitro renal toxicity of S-(1,2-dichlorovinyl)-L-cysteine

The major site at which vinyl cysteine conjugates exert nephrotoxicity is the proximal tubule. Since this is the site of all active anion and cation transport, tubule transport integrity was used to assess nephrotoxicity. Tubules were isolated from young rabbits to study the in vivo and in vitro nephrotoxicity of the conjugate, dichlorovinyl cysteine (DCVC). In vivo exposure to DCVC caused necrosis in the pars recta region of the proximal tubules (20-100 mg/kg ip) and a dose-dependent decrease in tubular active transport. Addition of DCVC to the perfused kidney and tubule suspensions resulted in similar decreases in tubular organic ion transport. At 0.01 mM DCVC, transport was similar to controls while 1 mM DCVC completely inhibited active accumulation of the organic ions. Thus kidney tubule active transport is similarly inhibited in vivo and in vitro by DCVC indicating that bioactivation of DCVC and inhibition of active transport occur directly in the renal tubule.

Morphometric, biochemical, and physiological assessment of perinatally induced renal dysfunction

Three chemicals, known either to alter renal development when administered during fetal development or to affect renal function when administered to adult rats, were administered to Sprague-Dawley rats at critical periods of renal development. Chlorambucil (CHL) was administered ip on d 11 of gestation at doses of 0, 3, and 6 mg/kg; nitrofen (2,4-dichlorophenyl p-nitrophenyl ether) (NIT) was given po on d 8-16 of gestation at 0, 4.17, 12.5, and 25 mg/kg . d; and mercuric chloride (MER) was given sc on postnatal d 1 at 0, 14, and 28 micrograms/pup. To assess the effects of these toxicants on the functional development of the kidneys, a diuresis test with and without antidiuretic hormone was applied on postnatal d 3 (PD 3); a hydropenia test on PD 6; and kidney weights, glomerular counts in midhilar cross sections, and the specific activity of renal alkaline phosphatase were determined on PD 3 and 6. Data from pups with obvious malformations of the kidneys was eliminated from the statistical analyses of the data so that emphasis could be placed on alterations of functional development in individuals with apparently morphologically normal kidneys. CHL retarded the growth and biochemical differentiation of the kidney at 6 mg/kg. Pups from this treatment groups showed an attenuated response to exogenously administered antidiuretic hormone. NIT impaired growth and altered renal morphology at a dose of 12.5 mg/kg . d and altered physiological responses in the absence of anatomical changes at a dose of 4.17 mg/kg . d. MER, at doses near the maximum tolerated, failed to alter any parameter, indicating that the very young animal differs markedly from the adult in response to that compound. The data indicate that relatively simple tests of renal function are useful in the detection of perinatally induced nephrotoxicity.

Rapid, automated measurements of urinary protein and glucose concentrations

Procedures are described for the quantitative determination of urinary protein and glucose concentrations using assay methodologies that are readily automated. Glucose was measured by the hexokinase method and protein by interaction with the dye Coomassie Brilliant Blue G-250. Both assays can be performed with a centrifugal analyzer. The linear range for the glucose assay was 10-500 mg/dl, encompassing the normal range of 10-30 mg/dl for glucose in rat urine. The linear range for the protein assay was 5-45 mg/dl, necessitating dilution of the urine (normal range for rats of 100-400 mg/dl) by a factor of 10. As with many other protein assay methodologies, response to gamma globulins was less than that to albumin. The procedures described herein require only minute quantities (5-10 microliters) of sample and are sufficiently simple and rapid to be used as screening procedures. Moreover, they provide quantitative results and are more sensitive than many of the more commonly used diagnostic tests for urine protein and glucose.

Changes in blood and urine composition from feeding polybrominated biphenyls to pregnant Holstein heifers

The toxicity of a commercial preparation of polybrominated biphenyl was determined in 24 pregnant Holstein heifers that were alloted randomly to one of four experimental groups given 0 (I), .25 (II), 250 (III), and 25,000 (IV) mg per day of fireMaster BP-6 for 60 days or until the animals became moribund. Clinicopathologic determinations were on day -1 prior to dosing, days 15, 30 and 60 during dosing, and following dosing on days 80, 110, 150, and 190 from start of dosing. In addition, samples were collected from moribund heifers of Group IV immediately prior to necropsy. Toxicity was not evident in heifers in Groups I, II, or III. Toxicity was induced in heifers in Group IV. Glutamic-oxaloacetic transaminase of serum was increased and calcium decreased as early as day 15 whereas significant increases in lactate dehydrogenase, urea nitrogen, and bilirubin, and decreases in albumin were not observed until day 30 in heifers of Group IV. Analysis of urine from moribund heifers of Group IV revealed moderate proteinuria and decreased specific gravity. Evaluation of clinicopathologic data has suggested that the polybrominated biphenyls fed were renal toxins with no clear evidence of hepatotoxicity.