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

AX5-2
Table AX5-2.1. Effect of Lead on Erythrocyte Morphology, Mobility, and Other Miscellaneous Parameters
Dose and Route of
Exposure Duration Species Blood lead Effect Authors
Pb nitrate
0–100 µM,
Free Pb 2+
0–20 µM,
In vitro
Pb nitrate
1.5 mM
In vitro
10 µM Pb,
as Pb acetate,
In vitro
100 µg/dL Pb,
10 mg/dL, Pb,
In vitro
2 µM Pb acetate
2 µM Pb
10 or 20 mM Pb
acetate, i.p. once a
week (100 or
200 µmoles)/ kg b.wt.
(a) Pb recovery
studies,
10 min
(b) Relationship
of free Pb 2+ to
added Pb,
20 min
Erythrocyte cell lysates from
humans
— Uptake and transport of Pb in erythrocyte and across erythrocyte cell
membrane under the influence of varying buffers and ions.
a. Pb can cross the membrane passively in either direction.
Influx and efflux show similar properties
b. Passive transport of Pb is strongly stimulated by HCO3 !
(bicarbonate)
c. Pb uptake is unaffected by varying the external concentrations of
Na + , K + , and Ca 2+
d. In RBC, Pb binds mainly to hemoglobin. The ratio of bound Pb
to free Pb 2+ in the cytosol is estimated 6000:1
1 h Human erythrocytes — Pb uptake and transport are studied in resealed erythrocyte ghosts.
a. Transport of Pb across erythrocyte membranes is passive
b. 90% of Pb uptake by erythrocytes is inhibited by drugs that block
anion transport, indicating the involvement of anion exchanges
c. Pb transport depends upon the presence of a second anion. In the
presence of HCO3 ! , the rate is stimulated in the order of ClO4 !