Energy balance in rabbit reticulocytes and its control by adenine nucleotides

Respiration, lactate formation and adenine nucleotide contents were measured in highly enriched rabbit reticulocytes using substrates and mitochondrial inhibitors to adjust different states of energy metabolism. With glucose as substrate rates of ATP synthesis generated via mitochondrial plus glycolytic ADP phosphorylation of 1,6 mumoles ATP/ml cells X min were calculated at cellular ATP/ADP ratios of 13 resp. phosphorylation potentials of about 8000 M-1. Titrations with inhibitors acting at different levels of mitochondrial ATP production (antimycin A, oligomycin, uncouplers 2,4 DNP or FCCP and combinations) revealed a stepwise decline of ATP/ADP ratios and phosphorylation potentials attaining values of 5 and lower, and 1100, respectively, comparable to observations without exogenous glucose. The inhibited phosphorylating respiration was compensated by apparently not fully stoichiometric stimulation of glycolysis resulting in calculated rates of ATP synthesis lowered towards 1,0 (oligomycin) and fluctuating between 1,3 and 2,0 (antimycin). Mutual linkages between ATP producing and consuming reactions obviously influenced by the inhibitory species themselves are suggested compatible with the assumption that multiple steady states in reticulocyte energy metabolism might be established.