Lecture
Most drugs and poisons that enter the body
form complexes or chemical compounds with proteins, lipoproteins, blood cells, and other cellular components. The strength
of the complexes or compounds formed in the body depends on the nature of the substances forming the complexes and on the type of bonds in these complexes or compounds.
When poisons interact with proteins and other substances
contained in the body, covalent,
ionic, hydrogen, ion-dipole, and dipole-dipole chemical bonds can form between the reacting compounds.
If ionic bonds arise between the poison and the protein substance,
a reverse reaction occurs rapidly, during which the compound of the protein substance with the poison decomposes into the components from which it was formed.
The interaction of poisons (mainly heavy metal ions) with the sulfhydryl groups of proteins leads to the formation of compounds with strong covalent
bonds. Such compounds hardly decompose into protein and metal ion.
Of the protein substances, albumin combines most actively with many poisons. Fibrinogen, γ-globulin and some other proteins bind with an insignificant amount of poisons.
Albumin binds well with alkaloids and their synthetic analogues at pH above its isoelectric point. Albumin also binds with barbiturates, fatty acids, sulfanilamide drugs, iodine-containing radiographic contrast agents, with basic and
acidic dyes, glycosides, and many other substances.
The interaction of proteins with fatty acids depends on the composition of these acids. As the number of carbon atoms in fatty acid molecules increases, the strength
of the bonds between proteins and these acids increases.
Zinc and copper ions bind well with γ-globulin. Metal
poisons (cations of certain metals) form strong complex and inner-complex compounds with amino acids, peptides, and proteins
Steroid
hormones bind with lipoproteins, some antibiotics – with nucleic
acids, carbon (II) oxide – with blood hemoglobin.
Only an insignificant amount of drugs and poisons entering the body do not bind with albumin and other proteins. These include
diethyl ether, glucose, urea, and so on.
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