Leukemogenic
Effect of Radioactive Phosphorus in Adult
and Fetally Exposed BALB Mice*
E. A. D. HOLMBERG, C. DOSNE DE PASQUALINI, E. ARINI, A. PAVLOVSKY, AND
S. L. RABASAt
(Seccion Leucemia Experimental,
Instituto
de Investigaciones
Hematologicas,
Academia Nacional
de Medicina,
Melo 3081 Buenos Aires, Argentina)
SUMMARY
The leukemogenic effect of radioactive phosphorus has been studied in adult females
and fetally exposed males and females of the BALB strain of mice.
The results obtained in this series of experiments indicate that fetally exposed fe
males are more sensitive to the effect of the agent than males (46.5 and 10.8 per cent,
respectively).
It has been observed that the incidence of leukemia in fetally exposed females is
negatively correlated with the dose. In males, on the other hand, there is no such cor
relation and the over-all incidence is not increased (10.8 per cent).
Adult and fetally exposed females submitted to sterilizing doses of @32
show the same
incidence of leukemias (42 and 36.3 per cent, respectively).
The experiments herein reported demonstrate that @32
is definitely leukemogenic.
It is known that radiophosphorus
kemia in mice (1, 4), but the available
afford precise data on the subject.
12) have
in rats
studied
the carcinogenic
and described
and squamous-cell
observed
@
The
(F32) induces leu
carded
literature
they
does not
Koletsky et al. (11,
activity
the appearance
of this agent
of osteosarcomas
carcinomas, but no leukemias were
in this species.
use
of
@32
human
final transformation
patients,
mainly
of complete
diseases
autolysis
or because
in the first 5 months
of
All animals which survived
more than 5 months and
were
not autolyzed
of death
at the time
Table 2.
All mice were observed
killed
either
when
until
evident
are included
spontaneous
signs
death,
of leukemia
in
or
were
present or at 2 years of age.
in those
vera, and its influence on the
of this condition into leukemia have
given rise to contradictory
because
life.
were
suffering from polycythemia
either
died of intercurrent
A complete autopsy
histologic
examinations
was performed in every animal
were carried
out routinely,
and
the
publications
(14, 15, 19—21). sections being stained with hematoxylin and eosin.
The term “leukemia―
is used in a broad sense, including
leukemias as such, lymphosarcomas,
and reticulum-cell
on adult and fetally cx
sarcomas, according to Dunn's classification (3).
Radioactive phosphorus was administered as NaPO4 by
the I.P. route, at the doses stated below.
METHODS
A group of pregnant mothers were given injections with
This series of facts makes particularly rewarding a further
experimental assessment of the leukemogenic effect of
p32• The
action
of this
isotope
posed mice is described herein.
MATERIAL
AND
60 @c.in order to study, 24 hr. later, the uptake of
Inbred BALB mice were used throughout these experi
ments.
The group
of “adults―
were females
that
had
fetal tissues compared
used was as follows. Each fetus
been treated by injection with radioactive phosphorus
when 3—5
months old. The group designated as “exposed and heated at 60°C. for 1 hr. in
and 0.1-mi.
during fetal life―includes 108 mice (71 females and 37 were homogenized,
males) out of 149 offspring (94 females and 55 males) of dried in an oven for 24 hr. The
supported
leucemia).
Atomica
by
Fundaleu
(Fundacion
para
combatir
la
We are indebted to the Comision Nacional de Energia
for supplying
us with
radioactive
phosphorus.
t From Instituto de Investigaciones Medicas, Rosario, Santa
Fe.
Received for publication June 2, 1964.
and mother was weighed
nitric acid; the solutions
samples of each were
counting was carried out
with a gas flow counter; as reference source, a @82
solid
standard (2.76 X 10@ mc.) was used.
pregnant mothers who were given injections of the radio
active agent between the 11th and 15th days of preg
nancy.
Forty mice (23 females and 17 males) were dis
* Partly
@32
in
with that of the mother; the technic
RESULTS
As can be seen in Table
1, when radiophosphorus
was
administered to adult BALB females, 15 out of 36 (42
per cent) developed leukemia, in an average latent period
of 16.7 months.
This incidence is significantly
higher
1745
Downloaded from cancerres.aacrjournals.org on June 15, 2017. © 1964 American Association for Cancer Research.
1746
Cancer Research
TABLE 1
INCIDENCE
OF Ps-INDUCED
FEMALE
LEUKEMIAS
BALB
IN
Vol. 24, November
1964
arc sin
ADULT
MIcE
60
Dose
of
miceLeukemias
(months)1euk@La)40
(,ic@)No.
(%)Latency
50
40
7
60
90
8
12015
640
13.60.34>0.10Total
21.3
14.6
43
37.5
30
5017.3
20
40
04
16. 216.7 187.34<0.01
8042
Controls36
TABLE 2
INCIDENCE
OF
P―-INDUCED
EXPOSED
The comparison
4.0
1.—Incidence
of leukemia
Ordinate,
percentage
of leukemias
i.a
in
@6t@495
fetally
[email protected].
exposed
expressed
females.
as arc sin
@/@j
abscissa, log dose. This slope is significant at the 0.01 level.
LEUKEMIAS
BALB
a@;
CHART
IN
FETALLY
MICE
between the incidence of leukemia in fetally
exposed females and males gives x2 = 12.20, P < 0.001. The com
parison between the incidence of leukemia in fetally exposed and
control females gives x' = 14.90, P < 0.001.
suavxv@
are sin
50@
su@vxv@
(Mo@eras)
(iionTas)
@0.
DOSE
(Mc.)[email protected]
LeuNo. of % leu
kemiaMw@
kemic
kemia2.5 mice
Non
leu
Leuof
@MALESMw@
mice%
kemicNo.
Non
20
40
@
5
10
20
40
60
10Total
907
4
9
75
23
16
66.8 21.1 19
7
42.8
18.3
21.5
19.6 20.5
50
18 22.2 20.3 18.3
1071 4018.820.21015.67
16
4
7
—
0
14.2 14
11.5
19.5
—
8
0
20
4
25
18
19
—
2
0
17
50 40— 1320.7
@
18
16.220.2
18.917.9
Controls71 8046.5
than that
@
(x2
of spontaneous
leukemia
@37
1015 16.316.8
19.1
2010.8
observed
in controls
CHART
0.;
2.—Incidence
of
tO
leukemia
13
in
[email protected]..
fetally
exposed
males.
Ordinate, percentage of leukemias expressed as arc sin
abscissa, log dose.
This slope is not significant
(P > 0.10)
per cent), while males had only 10.8 per cent, compared
with 10 per cent in controls.
Moreover, in the female group (Chart 1), when the
data are transformed into arc sin per cent and are plotted
against log dose, there is a significant negative correlation
percentage of leukemia induced and dose ad
7.43; P < 0.01). There is an apparent correlation between
between dose administered
and percentage of leukemia
induced which, for the dose range used, is not significant
(x2
0.34; P > 0.10).
Table 2 shows the results obtained when both male and
female BALB mice were exposed to @82
during fetal life.
Doses ranging from 2.5 to 90 sic. induced an over-all
percentage of 34.5 per cent leukemia, with a latency of
17.6 months.
The difference between P32-treated animals
and controls (both sexes), as tested by x2 is significant
at the 0.01 level.
It is interesting that in these series of experiments, no
correlation can be seen between dose administered
and
percentage
of leukemias
induced
when
both
sexes
considered together, nor is there any shortening
latent period (17.6 and 18 months, respectively).
are
in the
When these same results are further analyzed, taking
into consideration the influence of sex, it can be seen that
the females were more sensitive to the effect of P@, since
their
0.@
over-all
incidence
of leukemia
was 46.5 per cent,
which is a significant increase over their controls (16.2
ministered (r = —0.88;P
0.91).
The male group was similarly analyzed. Although
there seems to be a greater percentage of leukemias with
increasing doses, the small number of animals makes the
results of no statistical
P > 0.10).
The uptake of
significance
(Chart
2) (r = 0.56;
@32
in fetal tissues is approximately the
same as that of the mother; mean uptake for 36 fetuses =
1.284 ± 0.279 X 10—inc/mg of dry tissue; mean uptake
for 6 mothers = 1.091 ± 0.0097 X 10@ @tc/mgof dry
tissue.
DISCUSSION
The results described above show that
phosphorus induces leukemias in both adult
radioactive
and fetally
exposed female BALB mice.
At first glance these data seem to indicate that these
groups are equally sensitive to the effect of P@, since the
over-all incidence of leukemia in adult females and
fetally exposed mice of both sexes was 42 and 34.5 per cent,
Downloaded from cancerres.aacrjournals.org on June 15, 2017. © 1964 American Association for Cancer Research.
HOLMBERG et al.—Leukemogenic
respectively,
a difference of no statistical
significance.
Effect of
that
1747
@32
j@jMice
the opposite phenomenon
might be encountered
Even if the groups of the same sex (females) which received
the same dosage range (40—90nc.) are compared, the
percentages do not differ significantly (40 and 36.3 per
cent).
(Chart 2),
isotope on
designed in
The fact
These findings are opposite to those expected, since
radiophosphorus is supposed to be incorporated mainly
into cells with a high metabolic rate or with great pro
were born from mothers treated with the higher dose
range (Table 2) might suggest that the males were more
liferative
surviving were selected out as being more resistant. Al
though this would afford a possible explanation for the
activity,
such
as the
immature
or embryonic
cells, which obviously predominate in the fetuses.
These
results must be evaluated, however, by taking into con
sideration
fetus
the actual
is exposed;
amount
of radiation
the sex difference
to which
and,
each
consequently,
the hormonal influence; and the dose administered.
The pertinent studies have demonstrated that the con
centration of @32
j@about the same in mothers and fetuses.
The influence of sex on the incidence of leukemias and
lymphomas was pointed out many years ago (2, 7, 16-18).
Furthermore,
the effect of castration in mice of either sex
was
extensively
studied
by
several
investigators
(2, 5,
sensitive
as would be expected from the effect of the
the testes.
Further experiments
have beeii
order to clarify this point.
that a markedly larger number of females
to the lethal effect of the isotope,
difference
in the
incidence
of leukemia
so that those
between
females
and males exposed during fetal life, we have no proof to
support it since two groups of five pregnant mice which
were treated with injections, for another purpose, of
60 and 90 @c.gave birth to more males than females
(nineteen
and sixteen;
seventeen
and fifteen).
On the basis of the data reported above, we may con
elude that P@is a potent leukemogenic agent and that an
interesting
particularly
hormonal interaction
seems to be involved,
in the fetally exposed females.
9, 13, 16—18)in spontaneous as well as in induced leu
kemias. All these reports indicate that, in general, the
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Leukemogenic Effect of Radioactive Phosphorus in Adult and
Fetally Exposed BALB Mice
E. A. D. Holmberg, C. Dosne de Pasqualini, E. Arini, et al.
Cancer Res 1964;24:1745-1748.
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