Energy metabolism during the maturation of reticulocyte in vitro.

1. For the purpose to clarify the mechanism of the revolutional changes in energy metabolism during the reticulocyte maturation the metabolisms of glucose and of the pentose moieties of acid soluble nucleotides have been observed on rabbit reticulocytes incubated in vitro under various conditions. 2. The maturation of reticulocyte proceeds by using the energy produced by aerobic glycolysis and is arrested in the glucose deficient medium, but the pentose moieties of purine nucleotide and nucleoside added exogenously serve as the energy source for reticulocyte maturation even in the absence of glucose. 3. The test on the utility efficiency of glucose and inosine as the energy source for reticulocyte maturation revealed that glucose is used more effectively than the pentose moiety of inosine under aerobic condition, which is advantageous for reticulocyte maturation, and vice versa under anaerobic condition, which is comparable to the metabolism of mature red cell. 4. From these results it has been suggested that the maturation of reticulocyte is the process of degradation of RNA and acid soluble nucleotides supported by the aerobic glycolysis, where the degradation products of RNA and acid soluble purine nucleotides provide the purine derivatives as the material for ATP synthesis (36) and the pentose moieties as energy source. 5. A possible mechanism for the superior utility of glucose to nucleoside pentose during reticulocyte maturation and vice versa in mature red cell has been discussed. ∗PMID: 4239071 [PubMed indexed for MEDLINE] Copyright c ©OKAYAMA UNIVERSITY MEDICAL SCHOOL Acta Med. Okayama 22, 123-136 (968) ENERGY METABOLISM DURING THE MATURATION OF RETICULOCYTE IN VITRO Masanobu MIYAHARA, Satimaru SENO, Kenji HAYASHI, Takashi NAKATSUKA, Katsuko YOSHII and Jiro MUKAI Department of Pathology, Okayama University Medical School, Okayama, JaPan (Director: Prof. Satimaru Seno) Received for publication, April 16, 1968 The immature anucleate red cell, the mammalian reticulocyte, has all the cytoplasmic components of erythroblast, i. e., mitochondria (1, 2), endoplasmic reticulum or microsomes (2, 3), lysosomes and Golgi apparatus (4). I t matures to a red cell by losing gradually all these organellae with an active protein (hemoglobin) synthesis (4, 5). Therefore, the maturation process means a revolutinal change in energy metabolism losing the enzymes of tricarboxylic acid cycle and respiratory system (6-8), with concomitant loss of the enzymes for the de novo synthesis of purine nucleotides(9) retaining only low activities of the enzymes of anaerobic glycolysis and pentose cycle (10-12). The maturation of reticulocyte requires glucose as the energy source (13, 14), while mature red cell forms lactic acid by using purine nucleosides in the absence of glucose (15, 16). According to the observation of NAKAO and his cowarkers inosine enhances glycolytic ATP formation of mature red cell in the presence of adenine (17), and TSUBOI has proven that the intracellular level of adenine nucleotides is a limiting factor for the glycolytic process (18), in which the adenine nucleotides are decomposed rapidly to hypoxanthine in the absence of glucose (19). Similar phenomena were also observed in reticulocytes, i. e., the reticulocyte maturation proceeded with gradual accumulation of hypoxanthine(14) with gradual degradation of its RNA and acid soluble nucleotides. It was reported in the previous paper that the accumulation of hypoxanthine was stimulated by the treatment of respiratory inhibitor and uncoupler of oxidative phosphorylation with the inhibition of RNA degradation (19, 20). These results suggest that in the process of reticulocyte maturation the changes in energy metabolism, which ensues by the gradual loss of aerobic glycolysis, will be closely correlated to the nucleotide metabolism in the cell. The present experiment was designed to disclose the supposed correlation between acid soluble nucleotide metabolism and glycolysis in the