Earlier and more reliable detection of drug-induced kidney injury would improve clinical care and help to streamline drug-development. As the current standards to monitor renal function, such as blood urea nitrogen (BUN) or serum creatinine (SCr), are late indicators of kidney injury, we conducted ten nonclinical studies to rigorously assess the potential of four previously described nephrotoxicity markers to detect drug-induced kidney and liver injury. Whereas urinary clusterin outperformed BUN and SCr for detecting proximal tubular injury, urinary total protein, cystatin C and beta2-microglobulin showed a better diagnostic performance than BUN and SCr for detecting glomerular injury. Gene and protein expression analysis, in-situ hybridization and immunohistochemistry provide mechanistic evidence to support the use of these four markers for detecting kidney injury to guide regulatory decision making in drug development. The recognition of the qualification of these biomarkers by the EMEA and FDA will significantly enhance renal safety monitoring.

The Predictive Safety Testing Consortium's first regulatory submission to qualify kidney safety biomarkers revealed two deficiencies. To address the need for biomarkers that monitor recovery from agent-induced renal damage, we scored changes in the levels of urinary biomarkers in rats during recovery from renal injury induced by exposure to carbapenem A or gentamicin. All biomarkers responded to histologic tubular toxicities to varied degrees and with different kinetics. After a recovery period, all biomarkers returned to levels approaching those observed in uninjured animals. We next addressed the need for a serum biomarker that reflects general kidney function regardless of the exact site of renal injury. Our assay for serum cystatin C is more sensitive and specific than serum creatinine (SCr) or blood urea nitrogen (BUN) in monitoring generalized renal function after exposure of rats to eight nephrotoxicants and two hepatotoxicants. This sensitive serum biomarker will enable testing of renal function in animal studies that do not involve urine collection.

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SummaryBlood samples were taken from the retrobulbar venous plexus or the sublingual vein of male HanIbm:Wist rats to compare clinical pathology parameters between the two sampling techniques. By analogy with a pharmacokinetic study, blood was sampled six times during one day from unfasted animals. After 3 weeks of recovery, blood was taken from fasted animals on a single occasion. In addition, prolactin and corticosterone levels were determined to compare stress-related effects between the two sampling methods. Body weight development and food consumption were similar after single as well as after repeated blood sampling for the two blood sampling techniques. Haemotological evaluation showed a gradual decrease in erythrocyte count, haemoglobin concentration and haematocrit after repeated blood sampling. Repeated withdrawal of blood samples over 24 h corresponding to approximately 22 % of the total blood volume resulted in a decrease in red blood cell parameters by up to 30%. The withdrawal of approximately 10% of the total blood volume was associated with a decrease in these parameters by up to 10% and should not be exceeded for animal welfare reasons and to allow a reliable evaluation of data in a study. Repeated blood sampling was associated with an initial decrease in the number of white blood cells, mainly due to a reduction in lymphocytes; white blood cell counts were slightly increased one day after. The decrease in lymphocytes and the increase in neutrophils after repeated sampling were generally slightly more pronounced in the blood from the retrobulbar plexus than from the sublingual vein. Comparison of serum clinical chemistry data showed significantly higher activities of creatine kinase and aspartate aminotransferase in samples from the retrobulbar plexus. These findings suggest a higher degree of tissue damage with blood sampling from the retrobulbar plexus than from the sublingual vein. Despite a large inter-individual variability, higher mean values of prolactin on each occasion and corticosterone after a single sample in fasted animals indicate a higher stress associated with blood sampling from the retrobulbar plexus. KeywordsSingle and multiple blood collections; rat; retrobulbar plexus versus sublingual vein; clinical pathology; distress Blood samples from rats taken for determination of clinical pathology parameters or exposure levels of the test article in toxicity studies can be obtained by different methodsCorrespondence to: A. Mabl such as bleeding from the retrobulbar venous plexus (also described as retroorbital plexus or periorbital sinusl, puncture of the sublingual, saphenous or tail vein and tail tip amputation. Blood sampling from the retro-

Arteritis/polyarteritis occurs spontaneously in many species used in preclinical toxicology studies. In Göttingen minipigs, arteritis/polyarteritis is an occasionally observed background change. In the minipig, this finding differs in frequency and nature from age-related polyarteritis nodosa in rats or monkeys, and Beagle pain syndrome in dogs. In minipigs, it can be present in a single small- or medium-sized artery of an organ or a few organs and is most commonly recorded in the cardiac and extracardiac blood vessels, vagina, oviduct, rectum, epididymis, spinal cord, pancreas, urinary bladder, kidneys, and stomach. The etiology is unknown although it has been considered in minipigs as well as in rats, dogs, and monkeys to be possibly immune mediated. This background change is important with respect to its nature and distribution in the minipig in order to distinguish it from drug-induced vascular changes, which might occur in similar locations and have similar morphologic features. This review summarizes the morphology, incidence, and predilection sites of arteritis as a spontaneously occurring background change and as a drug-induced vasculopathy in the minipig, and also describes the main aspects to consider when evaluating vascular changes in Göttingen minipig toxicity studies and their human relevance.