title: Uptake of purine bases by Trypanosoma cruzi culture epimastigotes.
abstract: The uptake of adenine, guanine and hypoxanthine by Trypanosoma cruzi culture epimastigotes was studied over short time periods at 22 degrees C. The uptake process is concentrative, driven by the purine phosphoribosyltransferases and saturable at about 10 microM hypoxanthine and 1 microM adenine or guanine. Each purine base is apparently taken up by a separate route and the oxypurines are regulated in parallel. Adenine inhibits oxypurine uptake. When the material was incubated with guanine or hypoxanthine for more than 2 min, a decrease in the nucleotide/free base ratio was observed, indicating inhibition of the guanine and hypoxanthine phosphoribosyltransferases. The uptake rates during the ascending phase of uptake and of culture growth rates were of the order of 50 for hypoxanthine and 20 for guanine, relative to that of adenine. These rates were within the physiological range for cell growth in these cultures. During the phase of descending growth and decreased purine uptake activity rates, uptake was depressed to 20% of the rates required for the growth observed in the cultures. It is proposed that the decline in growth rate leads to an increase of the nucleotide pools in the cells which inhibit uptake. This depression may be a cause of the mitotic blockade which occurs during the stationary phase.
authors.forename: R C
authors.initials: RC
authors.lastname: Guimarães
authors.forename: W E
authors.initials: WE
authors.lastname: Gutteridge
mesh_terms: D000225:Adenine / Q000378:metabolism; D000818:Animals; D003470:Culture Media; D006147:Guanine / Q000378:metabolism; D007042:Hypoxanthines / Q000378:metabolism; D010430:Pentosyltransferases / Q000378:metabolism; D011687:Purines / Q000378:metabolism*; D014349:Trypanosoma cruzi / Q000378:metabolism*
chemical_list: D003470:Culture Media; D007042:Hypoxanthines; D011687:Purines; D006147:Guanine; D010430:Pentosyltransferases; C022484:purine phosphoribosyltransferase; D000225:Adenine