Induction of millimolar amounts of 5-phosphoribosyl-1-pyrophosphate in human erythrocytes by incubation in inosine-pyruvate-phosphate medium. A 31P-NMR study.
Incubation of human erythrocytes in inosine (10 mM), pyruvate (10 mM), phosphate (50 mM) and NaCl (75 mM) (IPP-medium)1 at pH 6.6 leads to a ca. 1000 fold increase in the concentration of 5-phosphoribosyl-1-pyrophosphate (PRPP) as identified and measured by 31P-NMR spectroscopy. PRPP accumulation is pH-dependent with a maximum at extracellular pH 6.60 and the maximum value of 1.3-1.6 mmol/l RBC is reached within one hour at 37 degrees C. PRPP accumulated despite high concentrations of 2,3-diphosphoglycerate (2,3-DPG), an inhibitor of PRPP-synthetase. The concentration of PRPP attained correlated with the intracellular concentration of inorganic phosphate (P1). Substitution of either adenosine or adenosine plus inosine for inosine in the medium (APP or A+IPP media) did not lead to NMR detectable accumulation of PRPP, despite the same high concentrations of intracellular P1. The lack of accumulation of PRPP in adenosine containing media may be related to the higher concentrations of nucleoside diphosphates induced in these media. These results show that neither 2,3-DPG nor PRPP itself inhibit the synthesis of PRPP in the human erythrocyte under these circumstances.
Dept. of Clinical Chemistry, Rigshospitalet, Denmark.
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Petersen
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Quistorff
D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007288:Inosine / Q000494:pharmacology; D009682:Magnetic Resonance Spectroscopy; D010428:Pentosephosphates / Q000378:metabolism*; D010754:Phosphoribosyl Pyrophosphate / Q000378:metabolism*; D010759:Phosphorus Isotopes; D011773:Pyruvates / Q000494:pharmacology*
D010428:Pentosephosphates; D010759:Phosphorus Isotopes; D011773:Pyruvates; D007288:Inosine; D010754:Phosphoribosyl Pyrophosphate