Affect Gas Exchange Research Articles

The mode of action of certain 3- and 5-nitropyridines and pyrimidines. III. Biochemical lesions in Trichomonas vaginalis

Some 5-nitropyridines and pyrimidines inhibit the growth of Trichomonas vaginalis in vitro and in vivo. They are detoxified by reduction to their corresponding amino analogs. The chemical 2-amino-5-nitropyrimidine has been used as a model compound to study the inhibitory pathway. During growth with inhibitory concentrations of 2-amino-5-nitropyrimidine the synthesis of DNA, RNA and protein paralleled multiplication. Polysaccharide accumulated in cells grown with inhibitor when maltose was used as the carbon source, but not when glucose was used. The organism normally stores carbohydrate as glycogen. The polysaccharide that accumulated in inhibited cells was shown by quantitative iodine staining to be less highly branched than glycogen. Addition of inhibitor to resting cells or cell-free extracts did not affect metabolism. Consequently, cells were grown for varying periods of time with inhibitor, and the metabolism of intact cells or dialyzed cell-free extracts compared to similar preparations of control cells grown simultaneously. Up to 2 hours growth with inhibitor did not affect gas exchange as measured with a Warburg apparatus, or dehydrogenation reactions as measured by following the reduction of triphenyl-tetrazolium chloride. Cells up to 2 hours of age were less active metabolically than older cells. After 3 hours growth with inhibitor, aerobic respiration and endogenous anaerobic fermentation remained intact, but anaerobic utilization of carbon sources was inhibited as were dehydrogenation reactions. It was found that the internal environment of inhibited cells was more aerobic than control cells. As compared to preparations from control cells, enzyme extracts of cells grown for 4 hours with inhibitor contained more glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase; the same amounts of aldolase and “malic enzyme”; and less malic dehydrogenase. The data have been interpreted as indicating that there is some sort of developmental cycle during the lag and early logarithmic phases of growth of T. vaginalis and that the inhibitor, by acting on an energy yielding mechanism, kills the cells by holding them in this early pattern. Growth with inhibitor did not affect the purine and pyrimidine base composition of RNA and DNA. For DNA, using cytosine as 1, these were cytosine:guanine:adenine: thymine as 1:.95:2.1:2.0. For RNA, they were cytosine:guanine:adenine:uracil as 1:1.2:2.6:2.2. The total cellular RNA of this organism is unique since its base composition closely mimics that of its DNA.