The radioisotope research laboratory at
NWRC provides powerful tools that allow scientists to evaluate more
precisely the wildlife management chemicals used by the Wildlife Services
Program. The Analytical Chemistry group at NWRC is one of the few in
the United States to employ these tools in wildlife studies. The tools
can accurately evaluate uptake, metabolism and excretion of compounds.
Additionally, in-vitro metabolism experiments provide scientists with
the ability to examine, step-by-step, metabolic processes that may be
Lab equipment such as the liquid scintillation counter, the flow scintillation
analyzer, and the biological oxidizer, can be used to analyze tissues
(solid or liquid) for radioactive (14C-labeled) chemicals. For example,
NWRC chemists have looked at the metabolism of DRC-1339 (3-chloro-4-methylaniline
hydrochloride) and alpha-chloralose as described below.
In DRC-1339 testing, two species (red-winged
blackbirds and dark-eyed juncos) were administered 14C-labeled DRC-1339.
Later, the feces and organs of the two test species were sampled and
analyzed for their radioactive content. By looking at individual organs
and tissues, scientists were able to easily determine the uptake, distribution,
and excretion of the chemical. Samples were taken at several time points,
so that rates of elimination could be determined. These rates are extremely
valuable for measuring potential secondary hazards.
Graph above shows concentration of 14-C DRC-1339
in various organs and tissues of red-winged blackbirds over time.The
radioactive DRC-1339 is present primarily in the gastrointestinal tract,
liver and kidney of exposed birds. Over time, the concentrations rapidly
decrease, except in the case of the kidney tissue, where concentrations
stay relatively constant.
Experiments with alpha-chloralose were conducted in a similar fashion.
The 14C- labeled alpha-chloralose was given orally to ducks. The rate
of elimination was determined by analyzing their feces for radioactivity.
Following a 7-day monitoring period, their organs and tissues were analyzed
to determine residue levels. The resulting data are being evaluated
to determine the possibility of petitioning agencies to permit expanded
use of this wildlife management tool.
Another set of valuable tools used in the radioisotope laboratory are
in-vitro metabolism experiments. Sub-cellular fractions are prepared
from the liver and kidneys of test animals. These cellular preparations
can provide a step-by-step look at the metabolic processes that may
be occurring after products are ingested. This provides a much clearer
picture of how chemicals used by Wildlife Services may cause the desired
effects in wildlife species. This understanding could lead to safer
or more effective uses of products.
The graph above shows the concentration of 14-C DRC-1339
in kidneys of juncos and red-winged blackbirds over time. When the two
bird species were exposed to radioactive DRC-1339, the less sensitive
junco rapidly excreted it and had very low residue levels left in the
kidneys. The more sensitive blackbird species had a kidney concentration
which remained relatively constant for the 24-hour exposure period.
David A. Goldade
Goal and Objectives