Page 445 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

412 SECTION | V Metals and Micronutrients

VetBooks.ir TABLE 23.1 Sources and Uses of Arsenic Uses

Sources
Valence/Form
Commercial uses Inorganic arsenic trioxide (13) Insecticide, cattle dip (0.18%)
and products
Inorganic sodium arsenite (13) Defoliant (highly toxic)
Inorganic copper acetoarsenite (13) Paris green—insecticide (emerald green)
Inorganic arsenic trioxide (13) Smelters
Inorganic sodium arsenate (15) Herbicide
Inorganic chromated copper Wood preservative
arsenate (15)
Inorganic lead arsenate (15) Insecticide and medicinal
Organic pentavalent (15) Monosodium methylarsenate (MSMA) and disodium methylarsenate
(DSMA) (highly toxic to cattle)
Ant bait
Leaded gasoline
Natural sources Ores, minerals, volcanoes
Ground water and soil
Medicinals Potassium arsenite (13) Fowler’s solution tonic/conditioner
Organic trivalent arsenical Thiacetarsamide—heartworm treatment in dogs
Organic pentavalent arsenical Tryparsamide—trypanosomiasis—old
Organic trivalent arsenical Melarsoprol—trypanocidal
Organic pentavalent arsenical Arsenical feed additives (arsanilic acid, sodium arsanilate, 3-nitro, 4-
hydroxyphenylarsonic acid)

arsenic are excreted more slowly and through the bile into arsenicals, and they may be considered as “vascular
the feces. poisons” (Hann and McHugo, 1960; Jubb and
Huxtable, 1993; Agency for Toxic Substances and Disease
Registry, 2007).
MECHANISM OF ACTION
Arsenates (15) are a little different. They are uncou-
Arsenite (13) reacts with sulfhydryl groups ( SH) of plers of oxidative phosphorylation. The inorganic penta-
proteins and inhibits the enzymes by blocking the active valents may substitute phosphate in this reaction. The
groups. The arsenite inhibits alpha-keto oxidases which result is an increase in body temperature. Organic penta-
contain dithiol groups and are involved in oxidation of valents have an unknown mechanism of action. There is
pyruvate. Lipoic acid, an essential coenzyme for pyruvic some thought that they may interfere with vitamins B 6
acid oxidase, and alpha-oxyglutaric acid oxidase are and B 1 , which may allow for the demyelination and sub-
inhibited by the arsenite. These play an essential role in sequent axonal degeneration that occurs.
the tricarboxylic acid cycle. Actively dividing cells hav- From experimental and clinical studies, evidence sug-
ing a high oxidative energy requirement are most suscep- gests that arsenic exposure is associated with various car-
tible to the effects of arsenicals. diopathologic effects, including ischemia, arrhythmia and
Arsenites induce vasodilation and can cause capillary heart failure. Possible mechanisms of cardiotoxicity
damage. The cellular integrity of the capillary is affected include oxidative stress, DNA fragmentation, apoptosis
by an unknown mechanism. Evidence of vascular and functional changes of ion channels (Alamolhodaei
instability is seen by the presence of congestion, edema, et al., 2015). Evidence also suggests that ROS mediated
and hemorrhage in most of the visceral organs of animals mitochondrial disruption, caspase activation, MAPK,
with acute poisoning. This same mechanism of action and P 53 are the pathways for arsenic induced apoptosis
occurs with inorganic arsenicals and with organic trivalent (Chen et al., 1998).