MATERIALS AND METHODS
Cerium-144 (III) chloride was obtained from the Oak Ridge National
Laboratory in a 1 M HCl solution.
The isotope as received contained no
other y-emitting impurities.
Dilutions were made with distilled water
to obtain a dose solution which was 0.2 M in HCl and contained 0.5
uci/ml +4*cecl3.
Adult male BALB/c mice 5 to 6 months old were maintained on a diet of
Purina laboratory chow with water ad Ztbttwn throughout the course of
the experiment.
Three groups of mice were used, one for each of the three fasting-feeding
regimens studies.
In each group, three mice were killed at 1, 2, 4, 8,
12, 16, or 24 hours after dosing.
The experiment thus involved a total
of 63 mice with 21 in each group.
These were:
I, fasted for 24 hours,
dosed, fasted thereafter; II, fasted for 24 hours, dosed, fasted for 8
hours, then given feed ad libitum; III, fasted for 24 hours, given feed
ad libitum for 4 hours before dosing, dosed, fasted again. The mice
were dosed by gavage with 0.1 uCi of 144Cecl; (0.5 pCi/ml) in 0.2 ml of
0.2 M HCl solution.
After dosing was completed, the mice were returned
to cages which were fitted with wire mesh bottoms to inhibit ingestion
of contaminated excreta.
The mice were asphyxiated with CO», the digestive tracts excised and sectioned (Figure 1), and the sections placed
into gamma counting tubes for !*4ce analysis.
Figures 2 and 3 show the
averages for three mice expressed as percent of the administered dose.
The administered dose standards and the intestinal sections were counted
in equivalent volumes of water under integral counting conditions in an
automatic gamma cowmter.
The 144ce activities of the gut sections were
counted in tubes that were filled to a 3-m]l total volume with water to
minimize the effect of changes in sample volume on the count rate of the
instrument.
RESULTS
Results of the experiment are shown in Figures 2 and 3.
The intestines
of groups I and II were essentially clear of !*4*ce activity
of the gut 12 hours after dosing. The group allowed to eat
before dosing and not thereafter had G.I. tracts containing
dissection, and the !**ce activity pattern of this group of
in all parts
4 hours
food on
mice exhibi-
ted an anomalous rise at later hours.
In addition, the gut transit time
of group III was about 12 hours longer than that of groups I and II.
Results obtained in fasted mice with cerium are indicative of rapid
transit of a soluble metal species along the empty gut with essentially
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