The energy metabolism of human-blood polymorphonuclear cells. Action of various effectors, except hormones.

Abstract

Pure and viable human granulocytes were prepared from peripheral blood, and incubated in a buffered saline medium. Glycolytic intermediates, adenine‐nucleotides, glycogen, glucose and oxygen consumptions, and lactate production were measured under standard (aerobiosis, pH 7.4) and modified conditions. Standard incubations allow the determination of mass‐action ratios, which localize regulatory steps at hexokinase, phosphofructokinase and glyceraldehyde‐phosphate dehydrogenase: phosphoglycerate kinase. Anaerobiosis results in an increased glucose consumption while lactate production remains normal, presumably because of an increased glycerolipid synthesis induced by the elevated NADH/NAD+ ratio. A positive crossover at phosphofructokinase level derives from ATP diminished content. 0.5 mM 2,4‐dinitrophenol induces an increased oxygen consumption, an ATP fall and a positive crossover at phosphofructokinase level with an augmented overall glycolysis. pH‐changes modify phosphofructokinase activity, as revealed by the positive and negative cross‐overs respectively observed at pH 7.80 and 6.85. 0.1 mM and 0.2 mM monoiodacetate inhibits overall glycolysis without increasing oxygen consumption; the NAD+/NADH ratio is notably decreased; an apparent positive crossover again appears at the phosphofructokinase step, but the decreased hexose‐monophosphate level may result from the diminished ATP, whose concentration is not far from the Michaelis constant of hexokinase. 2 mM to 20 mM sodium fluoride protects glycogen, inhibits glycolysis and dramatically increases oxygen consumption. 0.2 mM to 0.5 mM NaF‐activates glycolysis and glycogen breakdown, and inhibits oxygen consumption. 3 mM dibutyryl adenosine 3′:5′‐monophosphate increases glycogenolysis and induces two cross‐overs: a positive one at phosphofructokinase and a negative one at glyceraldehyde‐phosphate‐dehydrogenase: phosphoglycerate kinase level. The lipolytic action of 3′:5′‐AMP may explain those effects, by decreasing ATP/ADP and NAD+/NADH ratios. A comparison between over‐all glycolytic activities and cross‐over plots clearly indicates that granulocyte glycolysis is regulated at the hexokinase step by ATP availability as compared with Michaelis constant, at the phosphofructokinase level through an allosteric ATP inhibition, and at the glyceraldehyde‐phosphate‐dehydrogenase step by mass‐action of the NAD+/NADH ratio.