Important note: Information in this article was accurate in 1992. The state of the art may have changed since the publication date.
Pneumocystis carinii dihydrofolate reductase used to screen potential antipneumocystis drugs.
Antimicrob Agents Chemother. 1991 Jul;35(7):1348-55. Unique Identifier : AIDSLINE MED/92027609 Broughton MC; Queener SF; Department of Pharmacology and Toxicology, Indiana University; School of Medicine, Indianapolis 46202-5120.
Abstract:
Pneumocystis carinii was obtained in high yield from the lungs of immunosuppressed rats by rupturing mammalian host cells, washing away the soluble mammalian dihydrofolate reductase, and harvesting intact organisms in association with the mammalian plasma membranes. P. carinii dihydrofolate reductase, measured in the 100,000 x g supernatant from sonicated organisms, was obtained in yields ranging up to 62 IU per rat. The enzyme prepared in the presence of protease inhibitors was stable when frozen in liquid nitrogen. P. carinii dihydrofolate reductase differed from the mammalian enzyme in that the former was slightly inhibited by 150 mM KCl, whereas the latter was stimulated over twofold by 150 mM KCl. The standard assay for P. carinii dihydrofolate reductase contained 0.12 mM NADPH and 92 microM dihydrofolic acid. Under these conditions, the 50% inhibitory concentrations of the known inhibitors trimethoprim, trimetrexate, and pyrimethamine were 12 microM, 42 nM, and 3.8 microM, respectively. These standard compounds were also tested against dihydrofolate reductase from rat liver to allow an assessment of the selectivity of the drugs. Although it was the least potent, trimethoprim was the most selective. Pyrimethamine was more potent but was nonselective. Trimetrexate was extremely potent but was selective for mammalian dihydrofolate reductase. A series of experimental compounds was obtained from the National Cancer Institute and other sources through the Developmental Therapeutics Branch of the Division of AIDS at the National Institute of Allergy and Infectious Diseases. Among the first 87 compounds tested, 11 had 50% inhibitory concentrations below that of trimetrexate and 3 were more selective than trimethoprim. The most promising compounds in this original group were chemically related to methotrexate.
Keywords: Animal Anti-Infective Agents/*PHARMACOLOGY Drug Screening Female Liver/ENZYMOLOGY Lung/MICROBIOLOGY Methotrexate/ANALOGS & DERIVATIVES/PHARMACOLOGY Pneumocystis carinii/DRUG EFFECTS/*ENZYMOLOGY Pneumonia, Pneumocystis carinii/MICROBIOLOGY Rats Rats, Inbred Strains Structure-Activity Relationship Support, U.S. Gov't, P.H.S. Tetrahydrofolate Dehydrogenase/*ANTAGONISTS & INHIB JOURNAL ARTICLE
AEGiS presents published material, reprinted with permission and neither endorses nor opposes any material. All information contained on this website, including information relating to health conditions, products, and treatments, is for informational purposes only. It is often presented in summary or aggregate form. It is not meant to be a substitute for the advice provided by your own physician or other medical professionals. Always discuss treatment options with a doctor who specializes in treating HIV.
Important note: Information in this article was accurate in 1992. The state of the art may have changed since the publication date.
