The Toxicologist - Society of Toxicology

posure groups. However, the different exposure scenarios involving average styrene
exposure or peak exposures did not significantly alter the performance to any test.
Several factors could have influenced our results: definition of peaks, statistical
power or short exposure time.
1227 UTILITY OF C6-GLIOMA CELLS FOR EXPLORATORY
RISK ASSESSMENT OF MIXTURES OF INSECTICIDES.
D. M. Romero 1 , M. L. Kotler 1 and M. J. Wolansky 1, 2 . 1 Biological Chemistry
(Toxicology), ARG NRC / University of Buenos Aires School of Science, Buenos Aires,
Argentina and 2 ARG National Agency for Scientific and Technological Promotion,
Buenos Aires, Argentina.
Low levels of organophosphate (OP) and pyrethroid (PYR) insecticides may cooccur
in real environments and food products. Considering each compound independently,
these residue loadings may be considered safe for humans. However,
there is a consensus on the need of considering joint neurotoxicity data to improve
the accuracy of health risk estimates for these chemicals. We use a C6-glioma cell
culture as an exploratory in vitro system derived from rat nervous system aimed to
identify toxicologically relevant OP-PYR mixtures that may require cumulative risk
analysis efforts in in vivo models. First, 4 OPs (chlorpyrifos; acephate; methidathion;
diazinon) and 4 PYRs (type I: bifenthrin, tefluthrin; type II: α-cypermethrin,
deltamethrin) were examined in single-compound assays carried out in C6cells
after 4-48 hr exposure to each compound (0.1-250 μM). Threshold doses for
cell viability status were determined using optical microscopy and MTT assays. We
generated time- and dose-effect data, and ED15 values were computed from assays
conducted at t=24 hr. In general, micromolar exposures produced dose-related alterations
in cell viability at 24-48 hr. ED15s were 5-100 μM for PYRs and 5-30
μM for OPs. Second, we evaluated the effects of each insecticide on nucleus morphology
using Hoechst 33258 staining. We found dose-related increases in anomalous
nuclei shapes from the low μM range up. Last, we examined a mixture of equitoxic
levels of the 4 PYRs (1X mixture = Σ ED15) using the MTT assay. This
type-I/II mixture produced a dose-related, dual joint action at 24 hr: while addition
of individual effects was observed after exposure to the 1X mixture, dose-addition
was apparent at a 0.1X dose, i.e., well below the single-compound thresholds for
mitochondrial impact. We plan to evaluate other mixtures of insecticides in order
to select toxicologically relevant combinations for in vivo testing of cumulative
neurotoxicity.
1228 BARIUM INTAKE IN THE CANARY ISLANDS: A TOTAL
DIET STUDY.
C. Rubio, D. González-Weller, J. Gutiérrez and A. Hardisson. Toxicology,
University of La Laguna, La Laguna, Spain. Sponsor: A. Anadon.
Barium (Ba) is a divalent metal widely distributed in nature. Commercial uses make
it a potential food contaminant. The main sources of exposure for humans are food
consumption, water consumption, and inhalation. Ba appears in many common
foods at concentrations ranging from 0.21 to 11.0 mg/kg. Chronic exposure to this
element is often associated with toxic effects on the cardiovascular system of mammals.
Objectives: To quantify the concentration of Ba in 22 food groups as categorized
by the Canary Islands Nutrition Survey (ENCA, 2000) and to estimate the
total Ba intake in various segments of the population and the general population.
Material and Methods: A total of 440 samples were analyzed to determine the Ba
levels in various food groups. Ba was determined by Optical Emission Spectrometry
with Inductively Coupled Plasma (ICP-OES). Results: The average concentration of
Ba in the analyzed food groups was 0.65 mg/kg, implying an intake of 0.69 mg/day
of Ba in the adult population of the Canary Islands. All groups had detectable Ba levels.
Concentration levels ranged from 0.04 ± 0,04 mg/L in water to 5.21 ± 2,12
mg/kg in nuts. The food consumption patterns of various genders and age groups
were considered along with the Ba levels in the 22 food groups. The highest estimated
dietary intake levels were observed in the 45-54 age group, for both men and
women. Conclusions: This study demonstrates the need to assess, understand and
monitor both the levels of metals in various food groups and the dietary intake of the
population, in order to determine a safe intake level.
1229 HOUSE DUST-MEDIATED PAH EXPOSURES RELATED
TO SEALED PARKING LOTS MAY EXCEED DIETARY
INTAKES IN CHILDREN.
E. S. Williams 1 , B. J. Mahler 2 and P. C. Van Metre 2 . 1 Center for Reservoir and
Aquatic Systems Research, Baylor University, Waco, TX and 2 U.S. Geologic Survey,
Austin, TX.
Most assessments have indicated that dietary ingestion is the primary route of exposure
to carcinogenic polycyclic aromatic hydrocarbons (B2 PAHs; the seven PAH
compounds classified as probable human carcinogens by the EPA) for adults and
children. Studies have estimated that dietary B2 PAH intakes in children are 24.8
ng/kg/day or less, generally larger those associated with inhalation or non-dietary
ingestion of soil and house dust. Recent research has indicated that the use of coal
tar-based (CT) sealants on parking lots may be associated with increased concentrations
of B2 PAHs in settled house dust (SHD) in nearby living spaces (compared
with unsealed asphalt lots). We hypothesized that, for young children living in residences
adjacent to CT-sealed parking lots, exposures to B2 PAHs through ingestion
of SHD might surmount dietary intake as the primary route of exposure. Using default
exposure assumptions of 17.4 kg body weight and 10 and 50 mg/day for dust
ingestion rates, doses of 25.01 and 125.03 ng/kg/day B2 PAH were calculated for a
4 year old child living in a residence next to a CT-sealed parking lot, compared to
1.73 and 8.65 ng/kg/day for children living near unsealed asphalt parking lots.
According to this screening-level exposure model, children in living spaces adjacent
to parking lots sealed with CT-based products may be exposed to B2 PAHs primarily
through ingestion of SHD.
1230 DIRECT COMPARISON OF DRIED BLOOD SPOT (DBS)
ANALYSIS TO PLASMA AND WHOLE BLOOD
ANALYSIS IN TOXICOKINETIC STUDIES OF RATS.
L. Patrone 1 , G. Liu 2 , H. M. Snapp 2 , A. Batog 1 , J. Valentine 1 , R. S.
Mangipudy 1 , A. Tymiak 2 , Q. C. Ji 2 and M. E. Arnold 2 . 1 Drug Safety Evaluation,
Bristol-Myers Squibb, New Brunswick, NJ and 2 Bioanalytical Sciences, Bristol-Myers
Squibb, Lawrenceville, NJ.
Dried blood spot (DBS) analysis is a method gaining recognition for obtaining
drug exposure data. To evaluate the fidelity of DBS analysis compared to the accepted
practice of plasma analysis, comparison of the data obtained by these methods
is necessary. The primary objective of this presentation is to demonstrate how
BMS is exploring DBS toxicokinetic applications in rats by directly comparing
plasma to DBS from the same animal. In this study, 2 compounds were evaluated;
BMS-X and Omeprazole (a marketed proton pump inhibitor). Twelve rats were
evaluated for each compound, and 4 rats were used as controls to determine contamination
potential. 300 ul blood was drawn from each rat. Blood was spotted directly
from the collection tube onto the DBS cards in four 15 ul aliquots. The remaining
blood was centrifuged to obtain plasma. The ratio of blood to plasma
concentration was calculated and the “predicted” blood concentrations were obtained
by applying the ratio to the plasma concentrations. Toxicokinetic curves
were constructed by averaging the concentrations at each time point. Results obtained
from DBS, blood, and plasma were consistent while liquid whole blood
analysis was slightly more variable. Advantages of DBS include no need to centrifuge
samples, easy sample storage and shipment, small sample volume, and easier
sample preparation for analysis. Challenges include difficulties in assay development
for hydrophilic compounds. Carry-over and cross contamination during sample
analysis was not an issue. However, additional precaution is needed to prevent
this when an assay has a low lower limit of quantitation (LLOQ).
1231 DRIED BLOOD SPOT (DBS): A POTENTIAL
APPROACH TO MONITORING DRUG EXPOSURE IN
RAT FOETUSES.
S. Cinelli 1 , F. Pastori 2 , R. Cicalese 3 , S. Villa 4 and G. Oberto 1 . 1 Scientific
Direction, Research Toxicology Centre RTC, Pomezia - Rome, Italy, 2 Analytical
Chemistry, Research Toxicology Centre, Pomezia - Rome, Italy, 3 Toxicology, Research
Toxicology Centre, Pomezia - Rome, Italy and 4 Operative Direction, Research
Toxicology Centre, Pomezia- Rome, Italy. Sponsor: J. Brightwell.
Dried Blood Spot (DBS) is a promising technique to reduce blood sample volume
during non-clinical and clinical studies. For this reason the technique has been extensively
applied in the human paediatric population and could be used to monitor
foetal drug exposure during non-clinical reprotoxicity studies. For this experiment
oxacarbazepine was orally administered to pregnant rats and, following validation,
the DBS technique was used to evaluate placental barrier crossing, testing blood
from both dams and foetuses. Oxacarbazepine is an antiepileptic drug which is
known to cross the placental barrier. Analytical methods were validated using Ultra
Performance Liquid Chromatography and Tandem Mass Spectrometry (UPLC-
MS/MS) on plasma samples, applying the traditional extraction procedure, and on
whole blood spotted on DBS cards. Oxacarbazepine was administered to pregnant
Sprague Dawley female rats by oral gavage during the gestation period. Blood samples
were collected at necropsy from dams and foetuses. Blood taken from dams was
used to generate both plasma and DBS samples to compare performance of the two
procedures. Blood samples taken from foetuses were sufficient only to apply the
DBS technique. The results of the described experiment, demonstrating placental
transfer of oxacarbazepine, confirmed the applicability of DBS technique to evaluate
drug levels in dams and litters during reprotoxicity studies.
SOT 2011 ANNUAL MEETING 263