Korean J Parasitol.  1998 Sep;36(3):191-198. 10.3347/kjp.1998.36.3.191.

Changes in enzyme activity and expression of DHFR of Toxoplasma gondii by antifolates

• Baek EJ
• Nam HW

• KMID: 662563
• DOI: http://doi.org/10.3347/kjp.1998.36.3.191

Abstract

The responses to antifolates of Toxoplasma gondii were investigated by measuring the dihydrofolate reductase (DHFR) activity, quantity of DHFR mRNA, and single-strand conformational polymorphism (SSCP) pattern. Pyrimethamine (PYM) and methotrexate (MTX) were tested as antifolates. When T. gondii was treated with PYM, the viability was decreased by the increasing concentration of PYM, DHFR activity tended to increase as the passage proceeded, and the quantity of mRNA expressed was also increased according to passages. The viability of T. gondii was decreased by the increasing concentration of MTX, but it was maintained over 40% up to 100 microM MTX. DHFR activity was 77.4% in the 1st passage (1 microM). 82.2% in the 4th passage (10 microM), and 141.3% in the 7th passage (100 microM). But no changes were detected in SSCP pattern of T. gondii exposed to PYM and MTX, both. These results suggested that the response of T. gondii to PYM was regulated by transcriptional level and that, in MTX, the viability of T. gondii was derived from increasing DHFR activity.

MeSH Terms

Animal
Folic Acid Antagonists/pharmacology*
Genome, Protozoan
Human
Methotrexate/pharmacology
Mice
Mice, Inbred ICR
Mutation
Polymorphism, Single-Stranded Conformational
Pyrimethamine/pharmacology
RNA, Messenger/analysis
Reverse Transcriptase Polymerase Chain Reaction
Tetrahydrofolate Dehydrogenase/metabolism*
Toxoplasma/enzymology*
Toxoplasma/drug effects*
U937 Cells