Covalent Binding and other Mechanisms of Primaquine Toxicity

<p>A dose-dependent covalent binding of primaquine to mouse liver microsomal protein was found in both in vitro and in vivo studies. The binding in vitro was linear during the first 90 minutes of incubation and dependent on the concentration of mouse liver microsomal protein. The in vitro covalent binding was markedly enhanced by cofactors. Pretreatment of mice with phenobarbital, a cytochrome P450 inducer, increased the microsomal cytochrome P450 content and the in vitro covalent binding significantly. Binding was markedly inhibited when microsomal metabolism inhibitors (SK&F-525A, metyrapone and piperonyl butoxide), and sulfhydryl-contai ni ng compounds were added to the incubation system. Conversely, the inhibitory effect of inhibitors was not shown on in vivo binding; also induction with phenobarbital decreased the extent of covalent bindi ng in vivo. These findings pointed to the possibility that the extent of in vivo formation of metabolites which can bind covalently may be limited. However, injection of PQ (80 mg/Kg) into mice decreased the glutathione content of liver and erythrocytes, possibly through the formation of reactive metabolites.</p> <p>The NADPH-induced peroxidation of lipid of mouse mi crosomes and human erythrocyte membranes were markedly inhibited by PQ and 5H6DPQ (a PQ derivative), respectively. In contrast, PQ and its derivatives enhanced the NADPH-i nduced peroxidation of the lipids of intact erythrocytes.</p> <p>A significant amount of PQ metabolite(s) (formed by the mouse liver microsomal cofactor system) was bound covalently to the total protein of both normal and G6PD-deficient erythrocytes.. The net binding to the protein of G6PD-defi ci ent red cells was significantly greater than that to normal cells. A measurable amount of covalent binding of PQ metabolite(s) to human hemoglobin was also demonstrated. A small but significant amount of PQ metabolite(s) was also bound to human erythrocyte membrane protein. PQ and its derivatives decreased the amount of measurable sulfhydryl groups of G6PD-defi ci ent human erythrocyte membranes significantly but had no effect on the -SH groups of normal cell membranes. These results suggest that covalent binding of PQ metabolite(s) to human erythrocyte total protein and membrane protein as well as to hemoglobin may play an important role in hemolysis, particularly after cellular GSH and membrane sulfhydryl groups are depleted.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Pharmacology

Year

1983

Author dc:creator

• Chau Yau, Lucille S. K.

Contributors dc:contributor

• Ian M. Fraser
• David A. Hessinger
• Marvin A. Peters
• Allen Strother
• Robert Teel

• Pharmacology
• Toxicology
• Primaquine -- toxicity; Hemolysis -- drug effects

Statement dc:rights

• This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Language dc:language

English

Repository record dc:identifier

https://scholarsrepository.llu.edu/etd/830

OAI identifier oai:identifier

oai:scholarsrepository.llu.edu:etd-1931