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The specificity of the teratogenic effect of lead in the golden hamster
Life Sciences Vol. 10, Part II, pp. 35-39, 1971 . Printed in Great Britain
Pergamon Prese
THE SPECIFICITY OF THE TERATOGENIC EFFECT OF LEAD IN THE GOLDEN HAMSTERI V. H . Ferm and D . W . Ferm Department of Anatomy/Cytology, Dartmouth Medical School, Hanover, New Hampshire 03755
(Received 90 October 1970; in final form 23 November 1970)
The importance of lead as an environmental contaminant cannot be overstressed .
Of the many effects of this metal on biological
systems, one of the most important may be the impact it has on reproduction and its possible role in the etiology of congenital malformations .
In preliminary studies in experimental animals,
lead has been shown to cause embryonic death and resorption as well as certain specific developmental malformations when administered to pregnant mothers at a specific time in gestation (1) . The present study was undertaken to determine the effect of this metal upon mammalian development during the entire period of critical embryogenesis, as well as to determine its effect upon embryonic death in utero .
The hamster embryo is an especially
useful animal for these teratologic studies since it undergoes a rapid differentiation, telescoping the period of major organ differentiation into a twenty-four hour period between the eighth and ninth days of gestation (2) .
Lead is one of several elements which
have recently been shown to have serious potential for inducing severe developmental malformations in laboratory animals .
Thus,
cadmium (3), arsenic (4) and indium (5) have all been shown to reveal rather specific patterns of malformations when pregnant hamThis work was supported by research grants from the Easter Seal Research Foundation of the National Society for Crippled Children and Adults, Inc ., and USPHS grant HD 03298 .
35
38
Teratogenic Effect o~ Lead
Vol . 10, No. 1
sites are treated during the critical organogenetic period . Materials and Methods Pregnant golden hamsters of known gestational age were purchased from the Lakeview Hamster Colony .
The critical stages of
embryogenesis in this animal were divided into five periods during the eighth and ninth days of gestation (see Table I) .,
Each mater-
nal animal received a single intravenous injection in a manner previously described (6) of lead nitrate at a dose level of 25 mg/ kg or 50 mg/kg .
On the fifteenth day of gestation the animals were
killed and the fetuses recovered .
At this time, the number of
resorption sites were counted and recorded and the living embryos were examined for gross anatomical defects including rib malformations which can easily be determined at that time when the fetus is still alive .
After fixation in Bouin's fluid the fetuses were
dissected for gross internal malformations .
An examination of the
fetal rib cage for rib abnormalities was made at the time of sacrifice, and if malformations were suspected, the fetuses were fixed in alcohol, cleared and stained with alizarin red . Results The results of these experiments with lead are summarized in Table I .
As expected with most teratogens, both the embryonic re-
sorption rate and the malformation rate rise with increasing dos ages of lead .
Of principal interest, however, is the fact that the
teratogenic effect of lead is almost completely restricted to the tail region .
This particular malformation ranges from a minor
stunting of the tail bud to complete absence of the tail .
Four
cases of rib fusion were noted in embryos from mothers injected on the eighth day of pregnancy.
The data also indicates that the
resorption and malformation rate declined somewhat when the mater-
Vol. 10, No. 1
37
Teratogenic Effect oaf Lead
nal animals were injected late in the ninth day of gestation .
This
time of injection coincides with the latter part of the critical stage of embryogenesis in the hamster Dissections of fetuses following fixation revealed no grossly detectable abnormalities of abdominal or thoracic viscera .
Micro-
scopic studies were not done . TABLE I Time of Injection
Amount of Lead mg/kg
No . of Mothers
Total Number of Gestation Sacs
No . of Resorptions
No . of Live Fetuses
No . with Tail Abnormalities
Day 8 25 8 :00 a .m . 50
6 4
72 51
42 (58$) 40 (781)
30 11
22 (73$) 10 (91$)
Day 8 25 2 :00 p .m . 50
6 9
68 122
10 (15$) 112 (92$)
58 10
51 (88$) 10 (100$)
Day 8 25 8 :00 p .m . 50
6 5
63 60
28 (44$) S1 (85$)
35 9
33 (94$) 9 (100$)
Day 9 25 8 :00 a .m . 50
8 5
94 58
37 (39$) 58 (100$)
57 --
32 (56$)
Day 9 25 2 :00 p .m . 50
7 7
88 83
34 (39$) 61 (73$)
54 22
26 (48$) 9 (41$)
Discussion Unlike other metals and elements tested in the same animal model system, lead is very organ specific in its teratogenic effect . Cadmium, for example, induces a spectrum of abnormalities ranging from cleft lips and palates and exencephaly when the mothers are injected on the eighth day of gestation, to upper and lower limb bud defects when treatment is on the ninth day of gestation (7) . On the other hand, the injection of arsenic into pregnant hamsters
Teratogenic Effect ad Lead
g8
Vol. 10, No. 1
on the eighth day of gestation causes a high incidence of anencephaly, while injections on the ninth day produce a very marked increase in the number of rib malformations (8) . The specificity of the teratogenic effect of lead while unusual for other metals and elements tested is similar to the specific teratogenic effect of carbonic anhydrase inhibitors in hamsters, where only malformations of the limbs result from maternal treatment (9) .
In the case of the carbonic anhydrase inhibitors, the
limb malformations are found only in the upper limb buds and only the pre-axial portion of the limb is affected . These findings strongly support the suggestion that there must be a specific organ :teratogen effect (10) .
The specificity of this
effect can best be explained by an interference of the teratogen with a specific enzymatic event during development .
In this res-
pect it is of interest to note the findings of Millar et al . concerning the relationship of lead to
(11)
b-amino-levulinic acid
dehydratase in mentally retarded children and in lead-poisoned suckling rats .
Their findings suggest that biochemical abnormali-
ties of the brain may be associated with even moderate increases in the amount of lead in the blood .
Further studies on the rela-
tionship of levels of lead and ALA-dehydratase activity in embryonic systems during development seem to be indicated . References and Mol . Path . 7, 208 -
1.
V. H . Ferm, and S . J . Carpenter, J . Exp, (1967) .
2.
V. H . Ferm, Lab . Animal Care 17, 452 (1967) .
3.
V. H . Ferm, and S . J . Carpenter, Lab . Invest . 18, 429 (1968) .
4.
V. H . Ferm, and S . J . Carpenter, J, Reprod, and Fertil . 17, 199 (1968) .
5.
V. H . Ferm, and S . J . Carpenter, Toxicol . and Appl . Pharm . 16, (1967) .
Vol . 10, No. 1
Teratogenic Effect ad Lead
39
6.
V . H . Perm, and S . J . Carpenter, J . Exp . and Mol . Path . 7, 208
7.
V . H . Ferro, Roux Archiv .
8.
V. H . Ferro, A. Saxon, and B . W . Smith, Arch . Env. Health (in press) .
9.
W. M . Layton, Teratology (în press, 1970) .
(1967) .
_
(in press) .
10 .
V. H . Ferro, Roux Archiv . (in press) .
11 .
J . A . Millar, V . Baltistini, R . L . C . Caroming, F . Carswell, and A. Goldberg, Lancet ii, 695 (1970) .
Pergamon Prese
THE SPECIFICITY OF THE TERATOGENIC EFFECT OF LEAD IN THE GOLDEN HAMSTERI V. H . Ferm and D . W . Ferm Department of Anatomy/Cytology, Dartmouth Medical School, Hanover, New Hampshire 03755
(Received 90 October 1970; in final form 23 November 1970)
The importance of lead as an environmental contaminant cannot be overstressed .
Of the many effects of this metal on biological
systems, one of the most important may be the impact it has on reproduction and its possible role in the etiology of congenital malformations .
In preliminary studies in experimental animals,
lead has been shown to cause embryonic death and resorption as well as certain specific developmental malformations when administered to pregnant mothers at a specific time in gestation (1) . The present study was undertaken to determine the effect of this metal upon mammalian development during the entire period of critical embryogenesis, as well as to determine its effect upon embryonic death in utero .
The hamster embryo is an especially
useful animal for these teratologic studies since it undergoes a rapid differentiation, telescoping the period of major organ differentiation into a twenty-four hour period between the eighth and ninth days of gestation (2) .
Lead is one of several elements which
have recently been shown to have serious potential for inducing severe developmental malformations in laboratory animals .
Thus,
cadmium (3), arsenic (4) and indium (5) have all been shown to reveal rather specific patterns of malformations when pregnant hamThis work was supported by research grants from the Easter Seal Research Foundation of the National Society for Crippled Children and Adults, Inc ., and USPHS grant HD 03298 .
35
38
Teratogenic Effect o~ Lead
Vol . 10, No. 1
sites are treated during the critical organogenetic period . Materials and Methods Pregnant golden hamsters of known gestational age were purchased from the Lakeview Hamster Colony .
The critical stages of
embryogenesis in this animal were divided into five periods during the eighth and ninth days of gestation (see Table I) .,
Each mater-
nal animal received a single intravenous injection in a manner previously described (6) of lead nitrate at a dose level of 25 mg/ kg or 50 mg/kg .
On the fifteenth day of gestation the animals were
killed and the fetuses recovered .
At this time, the number of
resorption sites were counted and recorded and the living embryos were examined for gross anatomical defects including rib malformations which can easily be determined at that time when the fetus is still alive .
After fixation in Bouin's fluid the fetuses were
dissected for gross internal malformations .
An examination of the
fetal rib cage for rib abnormalities was made at the time of sacrifice, and if malformations were suspected, the fetuses were fixed in alcohol, cleared and stained with alizarin red . Results The results of these experiments with lead are summarized in Table I .
As expected with most teratogens, both the embryonic re-
sorption rate and the malformation rate rise with increasing dos ages of lead .
Of principal interest, however, is the fact that the
teratogenic effect of lead is almost completely restricted to the tail region .
This particular malformation ranges from a minor
stunting of the tail bud to complete absence of the tail .
Four
cases of rib fusion were noted in embryos from mothers injected on the eighth day of pregnancy.
The data also indicates that the
resorption and malformation rate declined somewhat when the mater-
Vol. 10, No. 1
37
Teratogenic Effect oaf Lead
nal animals were injected late in the ninth day of gestation .
This
time of injection coincides with the latter part of the critical stage of embryogenesis in the hamster Dissections of fetuses following fixation revealed no grossly detectable abnormalities of abdominal or thoracic viscera .
Micro-
scopic studies were not done . TABLE I Time of Injection
Amount of Lead mg/kg
No . of Mothers
Total Number of Gestation Sacs
No . of Resorptions
No . of Live Fetuses
No . with Tail Abnormalities
Day 8 25 8 :00 a .m . 50
6 4
72 51
42 (58$) 40 (781)
30 11
22 (73$) 10 (91$)
Day 8 25 2 :00 p .m . 50
6 9
68 122
10 (15$) 112 (92$)
58 10
51 (88$) 10 (100$)
Day 8 25 8 :00 p .m . 50
6 5
63 60
28 (44$) S1 (85$)
35 9
33 (94$) 9 (100$)
Day 9 25 8 :00 a .m . 50
8 5
94 58
37 (39$) 58 (100$)
57 --
32 (56$)
Day 9 25 2 :00 p .m . 50
7 7
88 83
34 (39$) 61 (73$)
54 22
26 (48$) 9 (41$)
Discussion Unlike other metals and elements tested in the same animal model system, lead is very organ specific in its teratogenic effect . Cadmium, for example, induces a spectrum of abnormalities ranging from cleft lips and palates and exencephaly when the mothers are injected on the eighth day of gestation, to upper and lower limb bud defects when treatment is on the ninth day of gestation (7) . On the other hand, the injection of arsenic into pregnant hamsters
Teratogenic Effect ad Lead
g8
Vol. 10, No. 1
on the eighth day of gestation causes a high incidence of anencephaly, while injections on the ninth day produce a very marked increase in the number of rib malformations (8) . The specificity of the teratogenic effect of lead while unusual for other metals and elements tested is similar to the specific teratogenic effect of carbonic anhydrase inhibitors in hamsters, where only malformations of the limbs result from maternal treatment (9) .
In the case of the carbonic anhydrase inhibitors, the
limb malformations are found only in the upper limb buds and only the pre-axial portion of the limb is affected . These findings strongly support the suggestion that there must be a specific organ :teratogen effect (10) .
The specificity of this
effect can best be explained by an interference of the teratogen with a specific enzymatic event during development .
In this res-
pect it is of interest to note the findings of Millar et al . concerning the relationship of lead to
(11)
b-amino-levulinic acid
dehydratase in mentally retarded children and in lead-poisoned suckling rats .
Their findings suggest that biochemical abnormali-
ties of the brain may be associated with even moderate increases in the amount of lead in the blood .
Further studies on the rela-
tionship of levels of lead and ALA-dehydratase activity in embryonic systems during development seem to be indicated . References and Mol . Path . 7, 208 -
1.
V. H . Ferm, and S . J . Carpenter, J . Exp, (1967) .
2.
V. H . Ferm, Lab . Animal Care 17, 452 (1967) .
3.
V. H . Ferm, and S . J . Carpenter, Lab . Invest . 18, 429 (1968) .
4.
V. H . Ferm, and S . J . Carpenter, J, Reprod, and Fertil . 17, 199 (1968) .
5.
V. H . Ferm, and S . J . Carpenter, Toxicol . and Appl . Pharm . 16, (1967) .
Vol . 10, No. 1
Teratogenic Effect ad Lead
39
6.
V . H . Perm, and S . J . Carpenter, J . Exp . and Mol . Path . 7, 208
7.
V . H . Ferro, Roux Archiv .
8.
V. H . Ferro, A. Saxon, and B . W . Smith, Arch . Env. Health (in press) .
9.
W. M . Layton, Teratology (în press, 1970) .
(1967) .
_
(in press) .
10 .
V. H . Ferro, Roux Archiv . (in press) .
11 .
J . A . Millar, V . Baltistini, R . L . C . Caroming, F . Carswell, and A. Goldberg, Lancet ii, 695 (1970) .