Adenine nucleotide metabolism and nucleoside transport in human erythrocytes under ATP depletion conditions.
The adenine nucleotides of human red cells were labeled by incubation of the cells with [3H]adenosine. Then, the cells were incubated in Tris-saline with various supplements that cause the loss of cellular ATP, and the degradation products were quantitated as a function of time of incubation at 37 degrees C. Incubation of the cells with 2.5 or 5 mM iodoacetate, iodoacetamide or 1 mM HCHO in combination with 5 mM KF and 50 mM deoxyglucose, 50 mM D-glucose or 10 mM inosine was most efficient in depleting the cells of ATP (100% in 0.5-1 h) without causing cell lysis. In iodoacetate- and iodoacetamide-treated cells practically all catabolism of ATP occurred via ADP----AMP----IMP----inosine----hypoxanthine with hypoxanthine accumulating in the medium. In HCHO-treated cells and in cells incubated in Tris-saline or in Tris-saline with deoxyglucose with and without KF, a substantial proportion of ATP (up to 50%) was catabolized via ADP----AMP----adenosine----inosine----hypoxanthine. Under all conditions, AMP deamination and IMP and AMP hydrolysis were rate-limiting reactions. IMP degradation was more rapid in iodoacetamide- and HCHO-treated than in iodoacetate-treated red cells. It was also more rapid in fresh than in outdated red cells, and it was inhibited by Pi. Treatment with iodoacetamide and HCHO under ATP-depletion conditions resulted in a 60-80% inhibition of uridine transport by the cells. Treatment with iodoacetate or deoxyglucose plus KF had only minor effects on nucleoside transport; thus, cells treated in this manner might be useful for studying the transport of adenosine and deoxyadenosine under conditions were their phosphorylation is prevented.
D000227:Adenine Nucleotides / Q000097:blood*; D000241:Adenosine / Q000097:blood; D000255:Adenosine Triphosphate / Q000097:blood*; D001692:Biological Transport / Q000187:drug effects; D003070:Coformycin / Q000031:analogs & derivatives / Q000494:pharmacology; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D007460:Iodoacetamide / Q000494:pharmacology; D007461:Iodoacetates / Q000494:pharmacology; D019807:Iodoacetic Acid; D007700:Kinetics; D015649:Pentostatin; D014316:Tritium
D000227:Adenine Nucleotides; D007461:Iodoacetates; D014316:Tritium; D003070:Coformycin; D015649:Pentostatin; D000255:Adenosine Triphosphate; D000241:Adenosine; D019807:Iodoacetic Acid; D007460:Iodoacetamide