EFFECTS
OF NUTRIENT SUPPLEMENTS ON BLOOD LEAD LEVELS
Drs.
Hongqiao Zhang, Xuetao Bai, Xingquan Zheng
Introduction
Many studies have
shown that the lead in the blood of a pregnant woman can cross the placenta
and enter the embryo/fetus, which is called 'prenatal lead exposure'.
Excessive prenatal lead exposure not only leads to abortion, stillbirth,
premature delivery and decrease of the height and weight of the newborn,
but also causes cognitive impairment of the affected child. The lead
burden level of women of childbearing age is tending to rise in China.
Reducing the children's prenatal lead exposure and effectively lowering
the lead burden level of women of childbearing age are both important
and imperative tasks in China.
It is well known
that the key to reducing children's prenatal lead exposure is to decrease
the high blood lead level of pregnant women through lead expelling therapy.
Although the usual clinical method of lead expelling therapy can effectively
decrease the lead burden, it is contraindicated in pregnant women. The
chelating agents usually used in lead expelling therapy are non-selective.
They not only cause the loss of some essential trace elements, but also
enhance the transplacental shift of lead, causing deformation of the
fetus. Therefore, researchers are getting more and more interested in
the diminishing effect of nutrients on lead toxicity. It has been reported
that vitamin B1, B6, metal elements Ca, Zn, Fe and some other nutrients
can reduce blood lead level, but there were few reports involving the
combined effectiveness of nutrients.
Three nutrient mixtures
listed below were investigated in their effectiveness of diminishing
lead from dams and their fetus.
1. Test solution
1?30mg/L vitamin B1, 35mg/L vitamin B6,
10mg/L folic acid, 0.1mg/L taurine in de-ionized water.
2. Test solution
2?A natural Chinese medicine rich in calcium,
6 g/L (=800mg ca2+/L)
3. test solution
3?1.8g/L Ca2+?0.3g/L
Zn2+?1.05g/L Fe3+?1.46mg/L
SeO32- in de-ionized water.
The pHs of above
mixtures are adjusted to 7.1 with NaOH.
Methods and Results
Trial 1:
Fifty female Wistar
rats weighted 120-140g were randomly divided into 5 groups. The test
schedule for the 5 groups were listed in table1. At 20th day of pregnancy,
the animals were sacrificed, and lead content in the blood, cerebrum,
cerebellum, liver, kidney and femur of dams, and lead content in fetal
brain, fetal liver, placenta, and the whole fetus were determined by
graphite atomic absorption spectrometry.
Table 1: The
test schedule of trial 1
| Days |
Group
1
(Negative
control)
|
Group
2
(Positive
control)
|
Group
3
(Test solution
1)
|
Group
4
(Test solution
2)
|
Group
5
(Test solution
3)
|
| 1-3 |
Adaptive
period |
| 4-32 |
Tap
water |
50
mgPb2+/L in de-ionized water |
| 33 |
Take
blood for lead determination |
| 33~40 |
Tap
water |
50
mgPb2+/L in de-ionized water |
Test
solution 1 + 50 mgPb2+/L |
Test
solution 2 + 50 mgPb2+/L |
Test
solution 3 + 50 mgPb2+/L |
| Start
mating with normal male rats to end of test |
There were no significant
difference among all the groups in food consumption, body gain of dam
before mating and fetus, number of fetus, and number of deformed or
absorbed fetus. Fig.1 and 3 illustrate the lead content in dam and fetus,
respectively. Fig.2 and 4 illustrate the effect of test solution on
lead content of dams and fetus compared to that of positive controls
(group 2). It indicates that only test solution 2 (group 4) lowered
the lead in blood, liver, kidney, cerebrum and cerebellum of dam and
in the brain and liver of the fetus and whole fetus and placenta of
fetus, significantly. Solution 1 (group 3) had only slight effectiveness
in lowering lead content in brain, and liver of fetus. Since in this
trial, the nutrient mixture was mixed with Pb before feeding it to rats,
we can not exclude that the effectiveness is due to combination of lead
with the components of the mixture, forming less absorbable Pb compound
in the digestive tract. Therefore, trial 2 was designed and conducted.
Trial 2
In this trial, only
nutrient mixture 2 was tested to ensure the significant effectiveness
on lowering lead burden showed in trial 1. Pb were given alternatively
every other day to exclude the combination of Pb with the components
in mixture in vitro. The test schedules of this trial are listed in
Table 2, and the results are illustrated in figure 5 as the percentage
of the
| Table
2 the test schedule of trial 2 |
| weeks |
Group
1
(negative
control)
|
Group
2
(positive
control)
|
Group
3
(test solution
2)
|
| 1~5 |
50
mg Pb2+/L in de-ionized water |
| |
1
take blood from each rats for Pb measurement,
2 8 rats were
sacrificed, and lead content in cerebellum, cerebellum, liver,
kidney and bone were determined.
|
| 6~11 |
Tape
water |
Tape
water and Pb containing water were drunk ad lib every other day,
alternatively |
Solution
2 and Pb containing water were drunk ad lib every other day, alternatively |
| |
All
rats were sacrificed, and lead content in blood, cerebrum, cerebellum,
liver, kidney and bone were determined. |
difference between
the control groups (negative control and positive control). It indicates
that mixture 2 can lower body burden of lead significantly. It decreased
61.7%, 93.2%, 72.5% and 84.4% of lead concentration in blood, liver,
brain and kidney, respectively, as compared to the positive control
group.
Nutrient supplements
might decrease body burden both in dams and fetus. Attention must be
paid to the adverse effect of unsuitable combination of nutrients. Test
mixture 2 is a hopeful substance for reducing body burden of lead, but
further investigation is needed before we can use it safely in human
beings.
Fig.1:
Lead content in tissues of dam
Fig.2:
Effectiveness of test mixtures as compared to positive control
Fig.3
lead content in tissues of fetus
Fig.4: Lead
burden as compared to positive control group
Fig
5: The effectiveness of test mixture 2 as compared to positive control
group.
