378
Trace Elements in Abiotic and Biotic Environments
taken up by phagocytic cells of the liver and spleen. Nevertheless, the bones are one
of the target organs of LAs. Because chemical properties of LAs are very similar, it
is plausible that their binding affinities to biomolecules, metabolism, and toxicity in
the living system are also very similar (Hirano and Suzuki 1996).
LAs entering the human body, due to exposure to various industrial works, can
affect metabolic processes. Trivalent LA ions, especially La 3+ and Gd 3+ , can interfere
with Ca channels in human and animal cells. They may also alter or even inhibit
the action of various enzymes. LA ions present in neurons can regulate synaptic
transmission, as well as block some receptors (e.g., glutamate receptors). Numerous
enzymes are affected by LAs: Dy 3+ and La 3+ block Ca 2+ -ATPase and Mg 2+ -ATPase,
whereas Eu 3+ and Tb 3+ inhibit calcineurin. In neurons, LA ions regulate the transport and release of synaptic transmitters, and block some membrane receptors, for
example, gamma-aminobutyric acid and glutamate receptors. It is likely that LA ions
significantly and uniquely affect biochemical pathways, thus altering physiological
processes in the cells of humans, animals, and plants (Pałasz and Czekaj 2000).
The use of LAs for medical purposes first began with their prescription as antiemetics. Several of the LAs are well known for their antimicrobial and anticoagulant
properties, and have been employed as antithrombic drugs (Jakupec et al. 2005).
Lanthanum carbonate is an efficacious noncalcium, nonresin phosphate binder
that is being increasingly used in patients with chronic kidney disease stage dialysis (Di Iorio and Cucciniell 2010). Cerium compounds are known for their uses in
topical burn treatments due to their bacteriostatic and bactericidal effects. Antiseptic
effects of Ce chloride, nitrate, and sulfate demonstrated particular susceptibility of
both gram-negative and gram-positive bacteria (which tend to coat burn wounds)
(Jakupec et al. 2005). Soluble LA salts are mildly toxic, whereas insoluble ones are
not (Emsley 2011).
LA nanoparticles (NPs) and nanorods have been widely used for diagnostic and
therapeutic applications in biomedical nanotechnology, due to their fluorescence
properties and pro-angiogenic to endothelial cells, respectively. Some LA elements
(Eu, Tb, Gd) as NPs play important roles in biology and medicine due to their unique
physical, chemical, and electronic properties (Patra et al. 2009).
LAs have the ability to accumulate in tumor tissues. As they provide various
radioisotopes, emitting α, β, or γ radiation, some of them even possess paramagnetic
properties and have become useful for anticancer diagnosis and therapy.
Human diets have not been monitored for LA contents, so it is not known how
much the average human takes in, but estimations show that the amount is only about
several micrograms per year, all coming from tiny amounts taken by plants.
57.7 ANIMALS
The distribution and excretion of LAs in laboratory animals is well known. When
LAs are administrated intravenously as salts, the main part of the dose (around
60%–80%) accumulates in the skeleton and the liver. It has been shown that the
higher the atomic number of the LAs, the higher the distribution ratio of the liver
versus the bone. The toxicity of LAs in rodents was dependent on the route of administration, their chemical forms, and the used animal model (Zielhuis et al. 2005).
Trace Elements in Abiotic and Biotic Environments
taken up by phagocytic cells of the liver and spleen. Nevertheless, the bones are one
of the target organs of LAs. Because chemical properties of LAs are very similar, it
is plausible that their binding affinities to biomolecules, metabolism, and toxicity in
the living system are also very similar (Hirano and Suzuki 1996).
LAs entering the human body, due to exposure to various industrial works, can
affect metabolic processes. Trivalent LA ions, especially La 3+ and Gd 3+ , can interfere
with Ca channels in human and animal cells. They may also alter or even inhibit
the action of various enzymes. LA ions present in neurons can regulate synaptic
transmission, as well as block some receptors (e.g., glutamate receptors). Numerous
enzymes are affected by LAs: Dy 3+ and La 3+ block Ca 2+ -ATPase and Mg 2+ -ATPase,
whereas Eu 3+ and Tb 3+ inhibit calcineurin. In neurons, LA ions regulate the transport and release of synaptic transmitters, and block some membrane receptors, for
example, gamma-aminobutyric acid and glutamate receptors. It is likely that LA ions
significantly and uniquely affect biochemical pathways, thus altering physiological
processes in the cells of humans, animals, and plants (Pałasz and Czekaj 2000).
The use of LAs for medical purposes first began with their prescription as antiemetics. Several of the LAs are well known for their antimicrobial and anticoagulant
properties, and have been employed as antithrombic drugs (Jakupec et al. 2005).
Lanthanum carbonate is an efficacious noncalcium, nonresin phosphate binder
that is being increasingly used in patients with chronic kidney disease stage dialysis (Di Iorio and Cucciniell 2010). Cerium compounds are known for their uses in
topical burn treatments due to their bacteriostatic and bactericidal effects. Antiseptic
effects of Ce chloride, nitrate, and sulfate demonstrated particular susceptibility of
both gram-negative and gram-positive bacteria (which tend to coat burn wounds)
(Jakupec et al. 2005). Soluble LA salts are mildly toxic, whereas insoluble ones are
not (Emsley 2011).
LA nanoparticles (NPs) and nanorods have been widely used for diagnostic and
therapeutic applications in biomedical nanotechnology, due to their fluorescence
properties and pro-angiogenic to endothelial cells, respectively. Some LA elements
(Eu, Tb, Gd) as NPs play important roles in biology and medicine due to their unique
physical, chemical, and electronic properties (Patra et al. 2009).
LAs have the ability to accumulate in tumor tissues. As they provide various
radioisotopes, emitting α, β, or γ radiation, some of them even possess paramagnetic
properties and have become useful for anticancer diagnosis and therapy.
Human diets have not been monitored for LA contents, so it is not known how
much the average human takes in, but estimations show that the amount is only about
several micrograms per year, all coming from tiny amounts taken by plants.
57.7 ANIMALS
The distribution and excretion of LAs in laboratory animals is well known. When
LAs are administrated intravenously as salts, the main part of the dose (around
60%–80%) accumulates in the skeleton and the liver. It has been shown that the
higher the atomic number of the LAs, the higher the distribution ratio of the liver
versus the bone. The toxicity of LAs in rodents was dependent on the route of administration, their chemical forms, and the used animal model (Zielhuis et al. 2005).