The Toxicologist - Society of Toxicology

294 LOW LEVEL OF LEAD CAN INDUCE
PHOSPHATIDYLSERINE-EXPOSURE AND
ERYTHROPHAGOCYTOSIS: A NEW MECHANISM
UNDERLYING LEAD-ASSOCIATED ANEMIA.
J. Noh, K. Kim, W. Jang, K. Lim, S. Kang, O. Bae and J. Chung. College of
Pharmacy, Seoul National University, Seoul, Republic of Korea.
Anemia is probably one of the most well-known toxic effects of lead. Previously,
lead-induced anemia was considered to be from the inhibition of δ-aminolevulinic
cid dehydratase (ALAD) participating in the heme iosynthesis. However, it was not
known whether lead could ffect the destruction of erythrocyte, another important
actor for anemia. In the present study, we demonstrated hat lead could accelerate
the splenic sequestration of rythrocytes through phosphatidylserine (PS) exposure
and ubsequently increased erythrophagocytosis. In freshly solated human erythrocytes,
Pb 2+ induced PS exposure at relatively low concentrations (~0.5 μM) by inhibiting
flippase, a key aminophospholipid translocase for the maintenance of PS
asymmetry and ATP depletion appeared to underlie this phenomenon. Abnormal
shape changes of erythrocytes and microvesicle generation, another trigger for the
erythrophagocytosis were also observed in the Pb 2+ -exposed erythrocytes. In vitro
data showed that human macrophage indeed recognized and phagocytosis PS-exposed
erythrocytes. In a good accordance with these in vitro results, the oral administration
of Pb 2+ increased PS exposure on erythrocytes in rat in vivo. In addition,
reduction of hematocrit and hemoglobin and increased spleen weight were
observed along with enhanced splenic sequestration of erythrocytes in the rats subchronically
exposed to Pb 2+ through drinking water. In conclusion, these results
suggest that Pb 2+ -induced anemia may be explained at least in part by increased PS
exposure on erythrocytes, erythrophagocytosis and splenic sequestration.
295 ACUTE ORAL LEAD BULLET FRAGMENT EXPOSURE
IN NORTHERN BOBWHITE QUAIL.
R. Kerr 1 , J. Hollady 1 , T. Jarrett 1 , S. D. Holladay 1 , B. Selcer 1 , B. Meldrum 2 , S.
Williams 3 , L. Tannenbaum 4 and R. M. Gogal 1 . 1 Department of Anatomy and
Radiology, University of Georgia, Athens, GA, 2 Department of Biomedical Sciences &
Pathobiology, Virginia Tech, Blacksburg, VA, 3 Poultry Diagnostic & Research Center,
University of Georgia, Athens, GA and 4 U.S. Army Center for Health Promotion &
Preventive Medicine, Department of Defense, Aberdeen, MD.
Lead (Pb) is a worldwide environmental contaminant known to adversely affect
multiple organ systems in mammalian and avian species. In birds, the primary
route of exposure is by oral ingestion of lead particles as grit or mistakenly as food.
Current data are lacking in the retention and clearance of Pb bullet fragments in the
bird’s GI tract while linking toxicity with blood Pb levels. In the present study,
Northern Bobwhite quail, fed a seed-based diet, were orally gavaged with Pb bullet
fragments (0, 1 and 5 fragments/bird) and evaluated for rate of fragment clearance,
changes in peripheral blood, renal, immune and gastrointestinal parameters. Based
on radiographs, the majority of the birds cleared or absorbed the fragments by 7
days with the exception of one 5-fragment bird, which took between 7-14 days.
Blood lead levels were higher in the males than females. Feed consumption, body
weight gain, packed cell volume (PCV), plasma protein concentration, δ-aminolevulinic
acid dehydratase (d-ALAD) activity were adversely affected by oral gavage
with 5 fragments in the males. However, Koilin degradation was observed only in
the 5 fragment female birds. Birds receiving a single lead pellet displayed depressed
d-ALAD suggesting altered hematologic function while birds acutely exposed to 5bullet
fragments exhibited greater morbidity.
296 ORAL LEAD PELLET EXPOSURE IN NORTHERN
BOBWHITE QUAIL: A 56-DAY STUDY.
R. M. Gogal 1 , R. Kerr 1 , J. Holladay 1 , S. D. Holladay 1 , L. Tannenbaum 2 , B.
Meldrum 3 and S. Williams 4 . 1 Department of Anatomy and Radiology, University of
Georgia, Athens, GA, 2 Department of Biomedical Sciences and Pathobiology, Virginia
Maryland Regional College, Blacksburg, VA, 3 U.S. Army Center for Health
Promotion and Preventative Medicine, Department of Defense, Aberdeen, MD and
4 Poultry Diagnostic and Research Center, University of Georgia, Athens, GA.
We recently reported in a 28 day study that acute oral lead (Pb) pellet (#9 shot) exposure
in Northern Bobwhite quail resulted in significant toxicity in birds ingesting
5 Pb pellets or greater. Birds that received a single lead pellet showed no overt clinical
signs of toxicity, but had sustained depressed plasma δ-aminolevulinic acid dehydratase
(d-ALAD) activity. In the present study, bobwhite quail, fed the same
seed-based diet, were orally gavaged once with Pb spent shot (0, 1, 2 and 3 pellets/bird)
and evaluated for 56 days for changes in feed consumption, weight gain,
peripheral blood Pb levels and physiology, renal, immune and gastrointestinal parameters.
Birds in the 3 pellet group showed a significant decrease in weight gain
which did not correlate with feed consumption. Mean blood Pb levels increased
proportionately to the number of pellets ingested at 7 days post exposure. Similar
to the previous study, male blood lead levels were significantly higher compared to
the females up to 14 days post exposure. These Pb blood levels declined weekly but
remained elevated throughout the study according to baseline data. Similar to the
previous study, the δ-aminolevulinic acid dehydratase (d-ALAD) activity decreased
significantly in all Pb pellet-treated birds, began to recover in the males but remained
lower than controls. Blood hematology, immune cytology and the other
endpoints were not remarkable. The results of this study support our previous findings
with regards to the 1 pellet birds and extend it by showing that birds exposed
to 2 and 3 pellets, although becoming transiently moribund, began to show clinical
signs of recovery 2 months post exposure.
297 ALUMINIUM TOXICITY AND ELEMENTAL
COMPOSITION CHANGES IN CAENORHABDITIS
ELEGANS.
K. E. Page 1, 2 , D. W. Killilea 3 , K. N. White 2 , C. R. McCrohan 2 and G. J.
Lithgow 1 . 1 The Buck Institute for Age Research, Novato, CA, 2 Faculty of Life
Sciences, University of Manchester, Manchester, United Kingdom and 3 Children’s
Hospital Oakland Research Institute, Oakland, CA.
Aluminium (Al) is a highly abundant crustal metal with known toxic effects in multiple
biological systems. The free-living terrestrial nematode Caenorhabditis elegans
(C. elegans) is widely used for toxicity and aging studies due to its small size, large
progeny numbers, short lifespan, and simple methods of genetic manipulation.
This makes C. elegans a good model to study the toxicity mechanism of Al in animals.
Aluminium exposures were carried out on agar plates with Al in the form of
Al(NO 3 ) 3 . Exposure of the nematode to Al results in altered elemental composition
of the organism with severe detrimental effects. Aluminium exposure alters the
course of normal aging in C. elegans from 1.9 mM. Aluminium negatively affects C.
elegans developmental progression from 3 μM Al, fertility at 30 μM Al, and body
size from 1.9 mM Al. The developmental delay phenotype caused by Al exposure
was observed even when exposure only occurred during embryogenesis. This transgenerational
toxic response poses questions concerning in utero Al exposure in humans.
At 4.8mM Al, the levels of not only Al, but a multitude of other elements in
the worms are altered. We have also found a set of genetic modulators of Al toxicity.
We have also found a set of genetic modulators of Al toxicity. These genes have
potential relevance in the metallostasis (metal homeostasis) of other metals, and a
sub set are key regulators of known stress resistance pathways. Knock-down of these
gene products alter the elemental profile of the worm. This provides a potential
mechanism of action for these genes in Al toxicity and general stress response.
298 BIOACCESSIBILITY-BASED READ-ACROSS
ASSESSMENT OF NICKEL COMPOUNDS FOR ORAL
SYSTEMIC TOXICITY.
R. G. Henderson 1 , D. Cappellini 2 , S. Seilkop 3 , A. R. Oller 1 and H. K. Bates 1 .
1 NiPERA, Inc., Durham, NC, 2 Kirby Memorial Health Center, Wilkes-Barre, PA
and 3 SKS Consulting Services, Siler City, NC.
A read-across assessment for oral systemic toxicity was undertaken for a series of
nickel (Ni) substances. Bioaccessibility can provide information regarding potential
bioavailability and subsequent toxicity such as acute and chronic oral toxicity and
reproductive toxicity. Twelve Ni-containing samples were extracted in synthetic
gastric and intestinal fluids. Acute oral toxicity studies in rats were conducted with
eleven of these substances to verify that the bioaccessibility data provide reasonable
estimates of systemic bioavailability and hence toxicity. The oral LD 50 data were
well predicted by Ni release data for each substance (R 2 =0.91). For substances with
existing oral LD 50 data, results were compared with their respective EU hazard classification.
For substances without LD 50 data, one sided lower confidence limits for
predicted LD 50 values were calculated. Results indicated with 95% confidence that
samples releasing 2000 mg substance/kg; samples releasing >76% available
Ni are expected to have an LD 50 between 200-300 mg substance/kg; and samples
with 48-76% bioaccessibility are predicted to have an LD 50 between 300-2000
mg substance/kg. When Ni substances were allocated into these three groups according
to bioaccessibility, the hazard classifications for systemic oral toxicity were
determined based on read-across from three data-rich nickel compounds. Samples
SOT 2011 ANNUAL MEETING 63