Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

AX5-127
Table AX5-8.2 (cont’d). Regulation of Bone Cell Function in Animals—Systemic Effects of Lead
Compound
Dose/Concentration
Duration Exposure
Route Species Effects Blood Level Reference
PbCl 2
0, 0.2, or 0.8%
1 or 2 wks
In diet
PbCl 2
0, 0.2, or 0.8%
1 or 2 wks
In diet
Pb acetate
1% for 10 wks or
0.001–1% for 24 wks
In drinking water
Chicks Compared with control animals, Pb exposure significantly increased intestinal calbindin
protein and mRNA levels in addition to plasma 1,25-dihydroxyvitamin D concentration.
The effect was present after 1 wk of exposure and continued through the second week. In
calcium-deficient animals increased plasma 1,25-dihydroxyvitamin D and calbindin protein
and mRNA were significantly (p < 0.05) inhibited by Pb exposure in a dose dependent
fashion over the 2 wk experimental period.
Chicks Dose dependent increases in serum 1,25-(OH2)D 3 levels (and Calbindin-D protein and
mRNA) with increasing dietary Pb exposure (0.1% to 0.8%) in experiments performed on
Leghorn cockerel chicks fed an adequate calcium diet.
Rat
Short term administration of 1% Pb resulted in significant increases in bone Pb. Total
serum calcium and ionized serum calcium were significantly decreased, as compared to
controls. Circulating levels of 1,25-(OH 2)D 3 were also decreased, though the rats were
maintained on a normal calcium diet (0.95%). In the long term study, a dose-dependent
increase in parathyroid weight occurred with increasing exposure to Pb in drinking water.
Short term (10 wks) exposure
Serum Calcium (mM) Ionized Calcium
(mM) 1,25(OH)2D 3 (pM)
Parathyroid Weight (µg/gland)
*p < 0.01
Long term (24 wks) exposure
Pb in water
0%
0.001%
0.01%
0.1%
1.0%
p < 0.01
Controls
2.42 ± 0.03
1.25 ± 0.03
232 ± 18.9
96 ± 34
Normalized Parathyroid
Weight (µg/g body wt)
0.50 ± 0.06
0.72 ± 0.25
0.81 ± 0.28
0.94 ± 0.27
0.81 ± 0.29*
Pb-exposed
2.32 ± 0.02*
1.15 ± 0.03*
177 ± 10.8*
178 ± 25*
1,25(OH) 2D 3 (pM)
241 ± 32
188 ± 27
163 ± 17
206 ± 24
144 ± 33*
None given Fullmer (1995)
None given Fullmer et al.
(1996)
Short term (10 wk)
study:
Control:
< 0.02 µg/l
Pb-exposed:
> 5µg/l
Szabo et al. (1991)