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

RENAL FUNCTION PARAMETERS OF HEALTHY CAPTIVE AND SEMICAPTIVE AMAZONIAN MANATEES (TRICHECHUS INUNGUIS)

Evaluating renal function is essential for managing captive wild animals, particularly threatened species like the Amazonian manatee (Trichechus inunguis) in rehabilitation and prerelease programs. A series of urine diagnostic tests, such as gross appearance, semiquantitative chemical analyses, microscopic review of sediments, and quantitative analyses of urea and creatinine, were performed in 57 free-catch urine samples. On the same occasion, 52 serum samples from the same individuals were analyzed for creatine kinase activity, creatinine, blood urea nitrogen, albumin, sodium, potassium, and chloride concentrations; serum symmetric dimethylarginine (SDMA) was measured for the first time in the species. Females had higher urine creatinine concentration (21.7 ± 11.8 mg/dl) and specific gravity (1.003 ± 0.003 mg/dl) than males (11.9 ± 8.5 mg/dl and 1.001 ± 0.002 mg/dl) (P < 0.01 for both). Males presented higher urine creatinine:urea ratio than females (24.8 ± 29.2 and 20.5 ± 29.2, respectively) (P < 0.05). Urine pH was lower in manatees from the semicaptive area (7.8 ± 0.6) than in manatees under human care (8.5 ± 0.6) (P = 0.02) using the benchtop pH meter but showed no difference between areas in the dipstick reaction (P = 0.71), given its lower sensitivity and narrower range detection. Furthermore, 18 and 75% of urine samples were positive for the presence of blood and/or nitrite, respectively, in the dipstick reaction, possibly because of sample contamination. Significant correlation was observed between serum blood urea nitrogen and urine urea concentrations (P = 0.02), and between serum and urine creatinine concentrations (P = 0.01). Serum SDMA did not differ between sex or between captive and semicaptive individuals. However, it positively correlated with urine (P = 0.02) and serum creatinine (P = 0.01) demonstrating its potential as a bioindicator of kidney function. The renal function of Amazonian manatees can be effectively assessed by urinalysis, especially when combined with serum biochemistry.

Polyphenolic grape stalk and coffee extracts attenuate spinal cord injury-induced neuropathic pain development in ICR-CD1 female mice

More than half of spinal cord injury (SCI) patients develop central neuropathic pain (CNP), which is largely refractory to current treatments. Considering the preclinical evidence showing that polyphenolic compounds may exert antinociceptive effects, the present work aimed to study preventive effects on SCI-induced CNP development by repeated administration of two vegetal polyphenolic extracts: grape stalk extract (GSE) and coffee extract (CE). Thermal hyperalgesia and mechanical allodynia were evaluated at 7, 14 and 21 days postinjury. Then, gliosis, ERK phosphorylation and the expression of CCL2 and CX3CL1 chemokines and their receptors, CCR2 and CX3CR1, were analyzed in the spinal cord. Gliosis and CX3CL1/CX3CR1 expression were also analyzed in the anterior cingulate cortex (ACC) and periaqueductal gray matter (PAG) since they are supraspinal structures involved in pain perception and modulation. GSE and CE treatments modulated pain behaviors accompanied by reduced gliosis in the spinal cord and both treatments modulated neuron-glia crosstalk-related biomolecules expression. Moreover, both extracts attenuated astrogliosis in the ACC and PAG as well as microgliosis in the ACC with an increased M2 subpopulation of microglial cells in the PAG. Finally, GSE and CE prevented CX3CL1/CX3CR1 upregulation in the PAG, and modulated their expression in ACC. These findings suggest that repeated administrations of either GSE or CE after SCI may be suitable pharmacologic strategies to attenuate SCI-induced CNP development by means of spinal and supraspinal neuroinflammation modulation.

Normal Ranges and Variability of Novel Urinary Renal Biomarkers in Sprague-Dawley Rats

Differences were examined between male and female Sprague-Dawley rats in basal levels of a wide range of urinary biomarkers, including 7 recently qualified biomarkers. The data were generated from urine samples collected on 3 occasions from untreated rats included in a study of the effect of gentamicin nephrotoxicity on urinary renal biomarkers, reported in a companion article in this journal (Gautier et al. 2014). The performance of multiple assays (9 singleplex assays and 2 multiplex platforms from Rules Based Medicine [RBM] and Meso Scale Discovery [MSD]) was evaluated, and normal ranges and variability estimates were derived. While variability was generally greater on the RBM platform than other assays, the more striking difference in the results from different assays was in magnitude. Where differences were observed between assays for an individual biomarker, they were seen in both sexes and consistent across samples collected at different time points. Differences of up to 15-fold were observed for some biomarker values between assays indicating that results generated using different assays should not be compared. For 8 biomarkers, there was compelling evidence for a sex difference. Baseline values in males were significantly higher than in females for total protein, β2-microglobulin, clusterin, cystatin-C, glutathione-S-transferase (GST-α), tissue inhibitor of metalloproteinases (TIMP-1), and vascular endothelial growth factor (VEGF); female values were significantly higher than that of males for albumin. The largest sex differences (male greater than female by 2- to 11-fold) were seen with β2-microglobulin, GST-α, and TIMP-1. These data add substantially to the limited body of knowledge in this area and provide a useful framework for evaluation of the potential relevance of sex differences in the diagnostic performance of these biomarkers.

Effect of feeding genetically modified Bt MON810 maize to ∼40-day-old pigs for 110 days on growth and health indicators

A total of 72 male weaned pigs were used in a 110-day study to investigate the effect of feeding genetically modified (GM) Bt MON810 maize on selected growth and health indicators. It was hypothesised that in pigs fed Bt maize, growth and health are not impacted compared with pigs fed isogenic maize-based diets. Following a 12-day basal period, pigs (10.7 ± 1.9 kg body weight (BW); ∼40 days old) were blocked by weight and ancestry and randomly assigned to treatments: (1) non-GM maize diet for 110 days (non-GM), (2) GM maize diet for 110 days (GM), (3) non-GM maize diet for 30 days followed by GM maize diet up to day 110 (non-GM/GM) and (4) GM maize diet for 30 days followed by non-GM maize diet up to day 110 (GM/non-GM). BW and daily feed intake were recorded on days 0, 30, 60 and 110 (n = 15). Body composition was determined by dual energy X-ray absorptiometry (n = 10) on day 80. Following slaughter on day 110, organs and intestines were weighed and sampled for histological analysis and urine was collected for biochemical analysis (n = 10). Serum biochemistry analysis was performed on days 0, 30, 60, 100 and 110. Growth performance and serum biochemistry were analysed as repeated measures with time and treatment as main factors. The slice option of SAS was used to determine treatment differences at individual time points. There was no effect of feeding GM maize on overall growth, body composition, organ and intestinal weight and histology or serum biochemistry on days 60 and 100 and on urine biochemistry on day 110. A treatment × time interaction was observed for serum urea (SU; P < 0.05), creatinine (SC; P < 0.05) and aspartate aminotransferase (AST; P < 0.05). On day 30, SU was lower for the non-GM/GM treatment compared with the non-GM, GM and GM/non-GM treatments (P < 0.05). On day 110, SC was higher for the non-GM/GM and GM/non-GM treatments compared with non-GM and GM treatments (P < 0.05). Overall, serum total protein was lower for the GM/non-GM treatment compared with the non-GM/GM treatment (P < 0.05). The magnitude of change observed in some serum biochemical parameters did not indicate organ dysfunction and the changes were not accompanied by histological lesions. Long-term feeding of GM maize to pigs did not adversely affect growth or the selected health indicators investigated.

Qualified kidney biomarkers and their potential significance in drug safety evaluation and prediction

The kidney is one of the major organs drug toxicity may target. Some renal safety biomarkers have been proposed to measure kidney injury and function accordingly. Despite the widespread use for diagnosis and monitoring of renal injury and function for decades, serum creatinine and blood urea nitrogen are nonspecific biomarkers with insensitive and delayed response in the clinical setting. There is an urgent need to identify and qualify novel kidney safety biomarkers that would be used to detect and predict drug-induced nephrotoxicity in preclinical toxicological studies, clinical trials and patient care in sequence. To do that, eight novel renal safety biomarkers have been well characterized and qualified for preclinical drug safety screening, and their clinical bridging validation is underway as well. Of them, some are used to detect or predict proximal tubular injury, and others are used to diagnose and monitor glomerular damage. Thus, measurement of a panel of kidney safety biomarkers in parallel would help maximally capture all potential safety signals for a more informative decision to be made in drug research and development as well as for optimal selection of the drug and its dose in clinical practice.

Effects of feeding Bt MON810 maize to sows during first gestation and lactation on maternal and offspring health indicators

A total of twenty-four sows and their offspring were used in a 20-week study to investigate the effects of feeding GM maize on maternal and offspring health. Sows were fed diets containing GM or non-GM maize from service to the end of lactation. GM maize-fed sows were heavier on day 56 of gestation (P< 0·05). Offspring from sows fed GM maize tended to be lighter at weaning (P= 0·08). Sows fed GM maize tended to have decreased serum total protein (P= 0·08), and increased serum creatinine (P< 0·05) and γ-glutamyltransferase activity (P= 0·07) on day 28 of lactation. Serum urea tended to be decreased on day 110 of gestation in GM maize-fed sows (P= 0·10) and in offspring at birth (P= 0·08). Both platelet count (P= 0·07) and mean cell Hb concentration (MCHC;P= 0·05) were decreased on day 110 of gestation in GM maize-fed sows; however, MCHC tended to be increased in offspring at birth (P= 0·08). There was a minimal effect of feeding GM maize to sows during gestation and lactation on maternal and offspring serum biochemistry and haematology at birth and body weight at weaning.

Effects of short-term feeding of Bt MON810 maize on growth performance, organ morphology and function in pigs

Male weanling pigs (n 32) with a mean initial body weight of 7·5 kg and a mean weaning age of 28 d were used in a 31 d study to investigate the effects of feeding GM (Bt MON810) maize on growth performance, intestinal histology and organ weight and function. At weaning, the pigs were fed a non-GM starter diet during a 6 d acclimatisation period. The pigs were then blocked by weight and litter ancestry and assigned to diets containing 38·9 % GM (Bt MON810) or non-GM isogenic parent line maize for 31 d. Body weight and feed disappearance were recorded on a weekly basis (n 16/treatment), and the pigs (n 10/treatment) were killed on day 31 for the collection of organ, tissue and blood samples. GM maize-fed pigs consumed more feed than the control pigs during the 31 d study (P < 0·05) and were less efficient at converting feed to gain during days 14-30 (P < 0·01). The kidneys of the pigs fed GM maize tended to be heavier than those of control pigs (P = 0·06); however, no histopathological changes or alterations in blood biochemistry were evident. Small intestinal morphology was not different between treatments. However, duodenal villi of GM maize-fed pigs tended to have fewer goblet cells/μm of villus compared with control pigs (P = 0·10). In conclusion, short-term feeding of Bt MON810 maize to weaned pigs resulted in increased feed consumption, less efficient conversion of feed to gain and a decrease in goblet cells/μm of duodenal villus. There was also a tendency for an increase in kidney weight, but this was not associated with changes in histopathology or blood biochemistry. The biological significance of these findings is currently being clarified in long-term exposure studies in pigs.

Trovafloxacin enhances TNF-induced inflammatory stress and cell death signaling and reduces TNF clearance in a murine model of idiosyncratic hepatotoxicity

Therapy employing the fluoroquinolone antibiotic, trovafloxacin (TVX) was curtailed due to idiosyncratic hepatotoxicity. Previous studies in mice showed that a nonhepatotoxic inflammatory stress induced by tumor necrosis factor alpha (TNF) synergized with a nonhepatotoxic dose of TVX to cause liver injury. The purpose of this study was to explore mechanisms by which TVX interacts with TNF to cause liver injury. TVX pretreatment prolonged the peak of plasma TNF after its administration. This prolongation of TNF by TVX was critical to the development of hepatotoxicity. The prolongation of TNF concentration in plasma was primarily due to reduced clearance when compared with secondary biosynthesis. TNF is cleared from plasma by binding to soluble TNF receptors (TNFRs) which are eliminated by the kidney; however, the plasma concentrations of soluble TNFRs were not reduced, and biomarkers of renal dysfunction were not elevated in TVX/TNF-treated mice. Two injections of TNF mimicked the prolongation of the TNF peak by TVX and caused liver injury, but injury was less severe than after TVX/TNF coexposure. TVX enhanced the induction of proinflammatory cytokines by TNF. Additionally, TVX sensitized Hepa1c1c7 cells to TNF-induced killing in a concentration-dependent manner and increased both potency and efficacy of TNF to activate effector caspases that were critically involved in cell death from TVX/TNF coexposure. In summary, TVX reduced the clearance of TNF independent of either receptor shedding or kidney dysfunction. Additionally, TVX interacted with TNF to enhance inflammation and sensitize hepatocytes to TNF-induced cell death.

Measurement of glomerular filtration rate in the conscious rat

INTRODUCTION

Glomerular filtration rate (GFR) is an important parameter for studying drug-induced impairments on renal function in rats. The GFR is calculated from the concentration of creatinine and blood urea nitrogen (BUN) in serum and in urine, respectively. Following current protocols serum and urine samples must be taken from the same animal. Thus, in order to determine time-dependent effects it is necessary to use for each time point one separated group of animals. We developed a statistical test which allows analyzing the GFR from two different groups of animals: one used for repeated serum and the other one used for repeated urine analysis.

METHODS

Serum and urine samples were taken from two different sets of rats which were otherwise treated identically, i.e. drug doses, routes of administration (per os or per inhalation) and tap water loading. For each dose group GFR mean, standard deviation and statistical analysis to identify differences between the dose groups were determined.

RESULTS

After determination of the optimal time points for measurements, the effect on GFR of the three reference compounds, furosemide, hydrochlorothiazide and formoterol, was calculated. The results showed that the diuretic drugs furosemide and hydrochlorothiazide decreased the GFR and the antidiuretic drug formoterol increased the GFR, as counter regulation on urine loss or urine retention, respectively.

DISCUSSION

A mathematical model and the corresponding algorithm were developed, which can be used to calculate the GFR, and to test for differences between groups from two separated sets of rats, one used for urine, and the other one for serum analysis. This new method has the potential to reduce the number of animals needed and to improve the quality of data generated from various groups of animals in renal function studies.

Assessment of renal injury in vivo

The ICH S7A (Safety Pharmacology for Human Pharmaceuticals) guidelines specify that potential adverse pharmacologic effects of a test substance on renal function should be evaluated in supplemental studies when there is a cause for concern (ICH, 2001). For the most part, this can easily be accomplished by examination of the appropriate analytes in urine and blood collected as part of the routine preclinical safety studies. This review will serve as an overview of the selection, interpretation and limitations of standard clinical pathology methods (serum chemistry and urinalysis) for assessment of renal function in such studies, as well as provide some information on emerging biomarkers of renal function.

Diagnostic relevance of qualitative proteinuria evaluated by use of sodium dodecyl sulfate-agarose gel electrophoresis and comparison with renal histologic findings in dogs

OBJECTIVE

To evaluate results of SDS-agarose gel electrophoresis (AGE) of urinary proteins for use in defining glomerular and tubulointerstitial derangements, investigate patterns of high-molecular-weight (HMW) proteins for differentiating among glomerular disorders, and assess low-molecular-weight (LMW) proteins as markers of severity of tubulointerstitial disease in dogs.

ANIMALS

49 dogs with increased serum creatinine concentrations or abnormal renal protein loss.

PROCEDURE

Urinary proteins were examined by use of SDS-AGE and differentiated on the basis of molecular weight. The HMW proteins (> or = 69 kd) were considered indicative of glomerular origin, whereas LMW proteins (< 69 kd) were of tubular origin. Renal specimens were examined by use of light microscopy. Glomerular and tubulointerstitial lesions were differentiated by use of the classification for the World Health Organization and semiquantitative grading, respectively.

RESULTS

Sensitivity of SDS-AGE was 100% for detection of glomerular lesions and 92.6% for tubulointerstitial lesions; specificity was 40% and 62.5%, respectively. Although HMW urinary proteins were not significantly associated with the type of glomerular lesion, LMW urinary proteins were significantly associated with the grade of tubulointerstitial damage. Detection of 12- or 15-kd proteins or both was highly indicative of a severe tubulointerstitial lesion.

CONCLUSIONS AND CLINICAL RELEVANCE

SDS-AGE of urinary proteins in dogs represents a noninvasive test with high sensitivity for identifying glomerular and tubulointerstitial damage, but low specificity limits its validity as a stand-alone test to differentiate between glomerular and tubulointerstitial lesions. The test is particularly useful for identifying dogs with advanced tubulointerstitial disease but cannot be used to characterize glomerular disorders.

Urinary enzyme evaluation of nephrotoxicity in the dog

Over the past 20 yr, increased attention has been directed toward evaluation of urinary enzymes as markers of nephrotoxicity in dogs because the technique is noninvasive and considered to be more sensitive than the more commonly used conventional tests of renal function. Urinary enzymes also have the potential of determining the primary site of renal damage because different sections of the nephron have a characteristic complement of enzymes. In dogs, increases in brush border enzymes, including gamma-glutamyl transferase and alkaline phosphatase, have been associated with renal proximal tubular damage, while increases in N-acetyl-beta-D-glucosaminidase have been observed in the early stage of renal papillary necrosis. Urinary enzymes have been particularly useful in detection of acute renal damage in dogs, specifically tubular damage: however, their corresponding value in providing information about chronic renal damage remains to be established. Although elevation of certain enzymes appears to be a relatively sensitive measure of nephrotoxicity in the dog, there is no current agreement regarding which enzyme assays are the most appropriate for routine use in safety assessment studies. In addition, elevation of a single enzyme is of limited diagnostic value in detection of renal damage because spurious increases in urinary enzymes sometimes occur in normal dogs. Therefore, if one wishes to conduct special assessment of nephrotoxicity in dogs, evaluation of several enzymes at multiple time points is needed to compensate for normal enzyme variation and to identify potential anatomic site selectivity of the toxin.

N-acetyl-beta-D-glucosaminidase as a marker of renal damage in hens

Urinary N-acetyl-beta-D-glucosaminidase (NAG) is an early physiological indicator of renal damage in several mammalian species. A study was conducted to confirm occurrence of NAG in hen urine, to establish baseline urinary NAG in laying hens, and to assess the feasibility of using the enzyme as a marker of renal damage in hens. Hy-Line hens were used in a completely randomized block design in the first part of the study. Urine was collected at 4 to 6, 6 to 10, 10 to 14, and 14 to 18 h, and serum at 4, 6, 10, and 14 h postoviposition, and assayed by spectrophotometry for NAG. Kidney tissue from additional hens was assayed histochemically for NAG. Serum NAG (range: 0.11 to 0.14 mU/mg protein) was found to be several orders of magnitude lower than urine NAG (6.44 to 12.27 mU/mg protein). Urine NAG increased from 4 to 6 h through 14 to 18 h, indicating that time of collection is critical in order to utilize the enzyme as a valid marker for laying hens. A preliminary study with five hens indicated that 10 d of treatment with liquid cholecalciferol (D3) supplement (three times the recommended level) were not enough to detect renal damage on the basis of significant changes in urine (NAG, but elevated urine NAG was detected at 40 d of D3-supplementation. Overall the results indicate that NAG in urine of laying hens is a potentially useful diagnostic marker of renal damage.

Gentamicin-induced nephrotoxicosis in lambs

Lambs injected with gentamicin sulphate remained bright and continued to eat, but their plasma creatinine and urinary microprotein concentrations and activities of alkaline phosphatase, gamma glutamyltransferase, leucine aminopeptidase, and N-acetyl-beta-glucosaminidase were significantly increased. Urinary creatinine and specific gravity were significantly decreased. The kidneys of lambs killed shortly after the last treatment with gentamicin were pale and oedematous and microscopic changes included marked tubular necrosis and dilation. Mild tubular dilation was the only lesion in lambs killed later. Reduced enzyme activity was observed histochemically in cells of the convoluted tubules. The lambs showed little clinical evidence of gentamicin toxicity, but the urinary enzyme activity and protein content were sensitive and reliable markers of renal injury, in agreement with the pathological findings. The lesions were different from those reported in naturally occurring tubular nephrosis of lambs.

Safety evaluation of lipase G from Penicillium camembertii

Lipase G, a partial glycerides eliminating enzyme produced by Penicillium camembertii, was subjected to safety evaluation studies to establish its safety when used as a processing aid in the food industry. The toxicological studies on the enzyme included a 90-day gavage study with rats, a mutagenicity study using bacteria, and a pathogenicity study using mice. The no-adverse-effect level from the 90-day gavage toxicity study was 2000 mg/kg body weight/day for rats. There was no evidence of mutagenic potential. The micro-organism was evaluated for pathogenicity using mice and classified as a non-pathogen. Results indicate that the production and use of lipase G may be regarded as safe for the enzyme production worker and the consumer.

Health status comparison by urinalysis (dipstick test) among four populations in Papua New Guinea

The health status of four populations depending on traditional subsistence in Papua New Guinea was compared by the dipstick test urinalysis. Conspicuous inter-population difference in the distribution of urinary pH was attributed to the levels of protein intake and the balances of sodium and potassium intake. The percentage of positive findings on protein differed by population along with the percentages of urobilinogen and bilirubin; the higher percentage of protein positives (12-16%) found in less urbanized populations suggests a high risk of hepatic and/or renal disorders in traditional societies. The very low percentage, 0.3 percent, of positive findings on glucose among 1,132 urine samples tested indicated that diabetes mellitus was not yet the major problem. Simultaneously, however, the fact that glucose positives were found only in the most urbanized villages indicates increasing risk of diabetes even in the traditional populations during future urbanization.

Biochemical assessment of cardiac 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

Species differences in metabolism, tissue localization, specificity and sensitivity for cardiac damage influence the choice of biochemical investigation used in the assessment of cardiotoxicity. The tests currently used in toxicological studies are broadly categorized herein as enzymes and other proteins, lipids and electrolytes; some limitations of these tests are also discussed.