This study directly demonstrates that cardiac troponin I (cTnI) is a sensitive, specific, and persistent biomarker in laboratory animals. Histopathological and pathophysiological cardiac changes in dogs, rats and mice correlated with increased serum cTnI with various cardiac inotropic agents, and cardiotoxic drugs and with cardiac arrhythmias, tachycardia, cardiac effusion with dyspnoea, and ageing. A comparison of six immunoassays for cTnI and cardiac troponin T (cTnT) to detect and monitor cardiac injury in a rodent model indicated that enzyme-linked immunosorbent (Life Diagnostics Inc and TriChem Resources Inc, West Chester, Philadelphia, USA) and Immulite (Diagnostic Products Corporation, Llanberis, UK) assays had low sensitivity and less than 1% of the dynamic range of Centaur (Bayer Healthcare Diagnostics, Newbury, UK) cTnI and Elecsys (Roche Diagnostics, Basel, Switzerland) and M8 (Bioveris Europe, Whitney, UK) cTnT assays. In dogs, however, the Immulite assay was effective and correlated with the Centaur. Serum concentrations were highly correlated but 10-fold lower for cTnT compared with cTnI with cardiac injury. Centaur assay also detected cTnI in myocardium from marmosets, swine, cattle, and guinea pigs, indicating it to be candidate cardiac biomarker for these species as well. Purified rat cTnI was 50% more reactive than purified human cTnI in the Centaur assay. In the rat, an age- and gender-dependent variation in serum cTnI was found. Male rats aged six and eight months had a 10-fold greater serum cTnI than age-matched females and three-month-old rats. These increases correlated with minimal histopathological change. Isoproterenol-induced serum cTnI increased up to 760-fold the minimal detectable concentration of 0.07 microg/L, within 4-6 h and decreased with a half-life of 6 h, with an expected return to baseline of 60 h. Severity of histopathological change correlated with serum cTnI during the ongoing injury.

SummaryThe performance of a clinical urinary test-strip reader Clinitek 200 was evaluated for dog and rat urines, in the context of pre-clinical toxicology studies. No major discrepancies were found between data generated by visual estimation or automatic measurement. Analysis of spiked samples showed good agreement between actual concentrations and Clinitek 200 responses for ketone bodies and glucose although a lack of sensitivity was found for the latter. Results for proteins showed over-or underestimation in dog and rat urines respectively at low concentrations, and overestimation at high concentrations in both species. Reproducibility of responses was excellent for ketone bodies, glucose and proteins but was weaker for haemoglobin and bilirubin. High bilirubin concentrations were found to interfere with the haemoglobin reaction. The pH measurements were found to be accurate only around pH 7. Specific gravity measurements were unreliable. Overall, the Clinitek 200 as a screening tool proved sufficiently reliable in the measurement of all parameters tested, with the exception of specific gravity. Keywords: Laboratory animals; Urinalysis; Test strip; Automated analysisThe clinical chemistry analyses performed in the course of pre-clinical toxicology studies, with

Haematological and clinical effects were evaluated after multiple blood samplings over 24 h in the laboratory rat and for up to 22 days after collection to determine the time required for a return to baseline values. Male and female Sprague-Dawley rats (n = 7/sex/group) were bled 4 times over 24 h and blood samples of 1.2, 1.6, 2.4 and 3.2 ml were taken. There were no adverse clinical signs and no statistically significant differences in body weight, body weight gain and food consumption. The acute effect on main haematological parameters of blood removal over 24 h consisted of reductions of red blood cell count, haemoglobin and haematocrit which were similar for blood removal exceeding 7.5% and less than 15% of circulating blood volume, and the reductions were positively related to the amount of blood loss beyond 15%. Time to recover to baseline values was also proportional to the initial blood collection volume and was estimated to range from 48 h for amounts from 5% to below 7.5%, 12 days for amounts from 7.5% to up to 20% and 19 days for amounts above 20%. Recommendations are made concerning suitable blood collection regimes.

1 This study assessed urinary creatine excretion as a marker for testicular atrophy. 2 Male rats received a single i.p. dose of 2-methoxyethanol at 0, 250 or 750 mg kg-1 and were sacrificed 2 d later. Urinary creatine and creatinine excretion were measured on days 0, 1 and 2. 3 Decreased testicular weights and histopathological assessment revealed dose-related testicular damage. 4 On day 1, at both doses of 2-methoxyethanol, urinary creatine levels increased and creatinine levels decreased, resulting in a dose-related increase in the creatine/creatinine ratio. On day 2, the creatine/creatinine ratio was elevated relative to controls, but was less marked than on day 1. 5 The study confirmed that creatine excretion is a potential marker for acute testicular damage.

Historically, blood samples have been taken by puncture of the orbital sinus under light ether anaesthesia. In the last decade, there was concern over the use of ether as an anaesthetic. Furthermore, in recent years, more attention has been focused on the need to improve current laboratory practices for the bene¢t of animal welfare. Exposure for 2 min to a CO 2 /O 2 mixture produced acute hyperkalaemia and changes in a range of haematological parameters. Hyperkalaemia in some individuals reached pathological levels when compared to values normally obtained from ether-anaesthetised animals. Together with published data, our ¢ndings indicate that the use of a 70:30 mixture of CO 2 /O 2 as an anaesthetic in rats is questionable. With iso£urane, the only consistent ¢ndings following exposure for 5 minutes were a slight downward trend in the red blood cell parameters and in potassium, and an increase in glucose. These changes probably represent an e¡ect of prolonged exposure to iso£urane. Therefore, to avoid variation in these parameters, the duration of exposure should be limited to 3 min. When comparing sublingual to retro-orbital blood sampling after 2 min exposure to 4% iso£urane, no major di¡erences were found in the plasma chemistry parameters examined. However, interference with plasma amylase levels following sampling from the sublingual vein has been suspected in one toxicity study. The acute e¡ect of blood removal over 24 h on the main haematological parameters consisted of decreases in red blood cells (RBC), haemoglobin (HGB) and haematocrit (HCT), which were similar for blood removal exceeding 7.5% but below 15% of circulating blood volume, and were positively related to the amount of blood loss beyond 15%. There were no biologically signi¢cant e¡ects on these parameters below 7.5%. Time to recover from the e¡ects of the bleed was also proportional to the volume taken, and was estimated to range from 48 h for amounts between 5% and 7.5%, 12 days for 7.5% to 20%, and 19 days for amounts above 20 %. The collection of up to 20% of the circulating blood volume over 24 h did not a¡ect the welfare of rats, as indicated by the absence of mortality and clinical signs and the lack of e¡ects on body weight and food consumption.