The Toxicologist - Society of Toxicology

involved the use of an acute inflammatory co-exposure model to characterize the
biochemical and physiological interactions between lipopolysaccharide (LPS) and
deoxynivalenol (DON) when administered at a low dose that alone would not
cause overt toxicity. Male rats were divided into 4 groups. Group 1 was administered
an IP dose of 10 mg DON/kg; group 2: 83 μg LPS/kg; group 3:10 mg DON
and 83 μg LPS/kg; group 4: 1 mL saline/kg. Animals were sacrificed at 3, 24, and
72 hours after dosing. The liver and brain were harvested and the free fatty acids extracted
and analyzed by gas chromatography. There was no significant change in the
brain. In the liver of group 1, palmitic acid decreased by 21.56% between 3 and 24
hr and increased 24.42% between 24 and 72 hr. In group 2, elaidic acid decreased
54.42% between 3 and 24 hr, and 6.88% between 24 hr and 72 hr. Stearic acid decreased
33.33% between 3 and 24 hr and 60.32% between 24 and 72 hr. There was
no significant change in group 3 and 4. This fatty acid profile of a decrease and increase
in palmitic acid with DON, and the decrease of elaidic and stearic acids with
LPS are indications of the participation in the palmitoylation process by the early
exposure of the cells to the toxins. Absence of active changes in the levels of affected
free fatty acids during co-exposure of LPS/DON over time suggests a disappearance
of defense mechanism against organ failure and innate immunity which warrants
further investigations on the crucial role of palmitoylation in infection and chemical
toxicity.
517 FEASIBILITY OF APPLYING DRIED BLOOD SPOT
(DBS) SAMPLING IN EXPLORATORY TOXICITY
STUDIES IN THE RAT.
W. Scott 1 , R. Hunter 2 , Z. Shen 2 , J. May 1 , L. Liu 1 , S. Vekich 2 , W. Huang 1 , R.
Rahavendran 2 and A. Sacaan 1 . 1 Drug Safety Research and Development, Pfizer Inc.,
San Diego, CA and 2 Pharmacokinetics Dynamics and Metabolism, Pfizer Inc., San
Diego, CA.
Rodent toxicity studies employ repeat blood sampling for toxicokinetic (TK) assessment
to accurately determine drug concentration and disposition. Typically this
is done using satellite groups to avoid the risk of compromising main study animals.
However, Dried Blood Spot (DBS) technology may enable the use of the
main toxicity animals for TK sampling. This is beneficial by reducing the number
of animals used on studies as well as enabling direct comparison of TK profile with
clinical findings in the same animals. In this study we evaluated the feasibility of
DBS technology using the main toxicology study animals.
Animals were divided into two groups and were administered vehicle once daily via
the oral route for 28 days; one group served as control and the other underwent serial
blood sampling up to 1.1 mL (total) over three sampling occasions (Days 1, 14
and 28). Clinical observation, histopathology and clinical chemistry were evaluated.
Data demonstrated that sampling up to 1.1 mL of blood did not lead to any
remarkable findings. We then conducted a second series of studies comparing TK
profiles of several compounds using plasma and whole blood - DBS. The majority
of the compounds tested had very comparable TK profiles further validating the use
of DBS. Lastly we conducted a study comparing the route of drug administration
and/or blood collection on the TK profile. In this study, Imatinib was administered
orally or intravenously to rats and blood was simultaneously sampled from three
different collection routes (jugular vein via an indwelling catheter, lateral tail vein,
and saphenous vein). Results revealed that there were no statistical differences in
the calculated TK parameters regardless of the route of blood collection. These data
are encouraging and support the use of the main study toxicology rats for TK sampling
thus eliminating the need for satellite TK groups in accordance with the 3R’s
initiative.
518 APPLICATION OF PREDICTION INTERVAL BASED
MIXED-EFFECT MODELS TO EVALUATE MONKEY
BODY WEIGHT CHANGE IN PRECLINICAL
TOXICOLOGY STUDIES.
D. Zhao 1 , R. Yeager 1 , Y. Lan 2 , C. Lin 2 and M. Duvall 1 . 1 Toxicology, Abbott,
Abbott Park, IL and 2 Statistics, Abbott, Abbott Park, IL.
Cynomolgus monkeys are an important and widely used species in preclinical toxicology
studies in drug research and development. Body weight effect and its correlation
to toxicity can be difficult to evaluate due to small sample size and/or large
inter- and intra-animal variability. Previously, pooled body weight data from more
than 550 individual control monkeys from 56 preclinical toxicology studies of 1-,
3- or 9-month duration were used to establish tolerance intervals in a mixed-effect
model. In the present study, the mixed-effect model was modified to incorporate
prediction intervals derived from the same control data set. These intervals provide
the normal bounds for body weight change from baseline in a control monkey over
time at a stated confidence level (dependent on study duration). In the present
study, body weight data, clinical observations, and associated pathology from more
than 500 compound-treated monkeys from 25 studies were analyzed. Although the
model is shown to be of limited utility when applied to shorter term studies (≤1month
duration), the robust data set and prediction intervals are a reliable aide in
interpreting the toxicological relevance of body weight effects in 3-month and 9month
monkey toxicity studies. Moreover, the results suggest that the model has
utility in quantitatively predicting the trend of individual body weight change in
order to make scientifically sound decisions during study conduct.
519 LONGITUDINAL COMPARISON OF SPONTANEOUS
OCULAR LESIONS IN THE NORMAL RAT AND MOUSE
ON CHRONIC TOXICOLOGY STUDIES.
K. Tenneson, N. Cicciu and M. Vézina. Toxicology, Charles River Preclinical
Services, Montreal, QC, Canada.
Ophthalmologic examinations are commonly conducted prior to the initiation of
dosing in rodent toxicology studies to confirm ocular health and are repeated
throughout the course of the study. We conducted a review of control animal data
for the Sprague-Dawley and Wistar Han rat, and the CD1 mouse from chronic toxicology
studies to determine the background incidence and progression of changes
with age. Corneal opacities were the most common observation in both rat strains
and mice ≤20 weeks of age and did not increase in incidence with age. There was a
low incidence of lens opacities in animals ≤20 weeks of age (10% in Sprague-
Dawley rats and 0% in CD1 mice). Lens opacities demonstrated a progressive increase
in incidence in both strains of rats and mice affecting up to 25% of rats and
75% of mice ≤ 2 years of age. Focal chorioretinal atrophy was observed in both
strains of rats and mice at a low incidence (approximate rate of ~1.5%) in prestudy
examinations and also developed during the course of treatment period appearing
as late as 1 year of age. In conclusion, we characterized findings on ophthalmologic
examinations over the life span of two strains of rats and mice on chronic toxicology
studies to facilitate the recognition of test article-related changes.
520 COMPARISON OF ANESTHETIC EFFECTS ON
ELECTRORETINOGRAMS (ERG) IN DOGS.
G. Glazier, D. Martel, T. Halle, S. Duval, T. Bryant and M. Vézina. Toxicology,
Charles River Preclinical Services, Montreal, QC, Canada.
The objective of this study was to investigate a suitable alternative for ketamine/xylazine
anesthesia, known for its minimal effects on the ERG, but also for prolonged
recovery times and potential drug interactions. The effect of 2-3% isoflurane (IM)
or 0.8 mg/kg/min propofol (PM), both in combination with 40 μg/kg medetomidine
on the ERG response in dogs was compared to that of 35.0 mg/kg ketamine/2.0
mg/kg xylazine (KX). Four dogs were anesthetized on up to 4 occasions
(minimum 4 days washout period) with each anesthetic combination. Each ERG
occasion consisted of a series of scotopic single flash stimuli following a dark adaptation
period of at least 1 hour (a. average of 5 single flashes at -30 dB, 10 seconds
between flashes; and b. -10 dB, 15 seconds between flashes; c. average of 2 single
flashes at 0 dB (2.0 cd-s/m2), 120 seconds between flashes). Amplitudes with IM,
were decreased (A and B waves) and delayed (A wave only for -10 and 0 db) compared
to those obtained with KX. In contrast, PM amplitudes were generally increased
(with the exception of the A wave for the 0 db test) with a faster response
time for the B-wave for all tests. PM had a milder inhibition on the A-wave at 0 db
with a 10% reduction in amplitude and 10% increased implicit time compared to
the IM at 42% reduction of amplitude and 34% increased implicit time. Ranges for
amplitude and/or implicit time with IM were generally more variable than those
with KX and PM, whereas PM ranges were more similar to those obtained with the
KX. PM produced less variable data than IM as well. In conclusion, PM produced
the most similar data to those obtained with KM, but with an increased sensitivity
to the light stimulus, and was considered a suitable alternative anesthetic agent for
ERG testing when KX anesthesia is contraindicated. In addition, IM anesthesia is
not recommended for ERG data collection.
521 APPLICATION OF THE rasH2 MOUSE IN
CARCINOGENESIS AND BIOMARKER STUDIES.
Y. Shimamura 1 , R. Arai 1 , A. Sunohara 1 , F. Baba 1 , K. Urano 2 , H. Tsutsumi 2 ,
M. Ito 2 , A. Hirayama 1 , M. Sugimoto 1 , T. Soga 1 , T. Nomura 2 and M. Tomita 1 .
1 Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan and
2 Central Institute for Experimental Animals, Kawasaki, Kanagawa, Japan.
The rasH2 mouse is a hemizygous transgenic animal used in 26-week carcinogenicity
studies for regulatory purposes. We investigated the metabolite profile of this
mouse model as a key factor in carcinogenesis using high throughput capillary electrophoresis/time-of-flight
mass spectrometry (CE-TOFMS). N-methyl-N-nitrosourea
(MNU, 37.5 mg/kg) was administered intraperitoneally to rasH2 mouse
SOT 2011 ANNUAL MEETING 111