Abstract
Summary
Rat liver glucose 6-phosphate dehydrogenase (G6PD) and malic enzyme (ME) activities were increased by starvation-refeeding to levels above those found in rats fed ad libitum. The increases in enzyme activities above ad libitum-fed levels were prevented by 8-azaguanine and 6-aza-uridine, but not by 2-azauridine. Blood insulin levels were not affected at the time studied. Two aza analogs, 8-azaadenine and 5-azacytidine, proved to be too toxic in this type of studies. Since 8-azahypoxanthine, 8-azaxanthine and 5-azauracil were neither effective in preventing the enzyme overshoot, nor toxic to the animals, it was concluded that the toxicity to the animals of 8-azaadenine and 5-azacytidine is due to the compounds themselves rather than to their breakdown products.
The author wishes to thank the following people: C. D. Berdanier, P. B. Moser, and S. K. Diachenko who collaborated with the author on experiment 1; O. E. Michaelis, IV and C. S. Nace for technical assistance; and R. F. Doherty and R. Sanchez (the latter of Terra-Marine Bioresearch) for advice concerning the conversion of 5-azacytidine.
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