Pyruvate kinase deficiency in dog and human erythrocytes: effects of energy depletion on cation composition and cellular hydration

A hypothesis of haemolysis in haemolytic anaemias associated with enzymopathies

A feature of a previously proposed mechanism of erythrocyte shape control is a control of the shape by the Donnan equilibrium ratio. An enzymopathy of the glycolytic pathway and nucleotide metabolism could alter the Donnan ratio, since it alters levels of phosphate intermediates and of end-products carbonic gas (CO(2)) and ammonia gas (NH(3)) which are ionized at the erythrocyte pH. Thus, a hypothesis of haemolysis in haemolytic anaemias associated with enzymopathies of the glycolytic pathway and nucleotide metabolism would be that it results from an inhibition of the mechanism by a modification of the Donnan ratio. This hypothesis seems plausible as it would explain coherently observations in these haemolytic anaemias.

Characterization of phosphofructokinase-deficient canine erythrocytes

Dogs homozygously affected with muscle-type phosphofructokinase (PFK) deficiency had about 20% of normal erythrocyte PFK activity and exhibited a compensated haemolytic anaemia. Erythrocyte glucose-6-phosphate and fructose-6-phosphate concentrations were increased and dihydroxyacetone phosphate and 2,3-bisphosphoglycerate values were below normal in affected dogs. Other intermediates distal to the PFK step were not significantly below normal and fructose-1,6-bisphosphate was even above normal. Erythrocyte ATP was higher than normal in affected dogs owing to the reticulocytes present. Abnormal adenylate metabolism was demonstrated by low ATP/AMP and ADP/AMP ratios and the inability to maintain ATP content when affected erythrocytes were incubated with cyanide. Glucose-1,6-bisphosphate content was normal, and fructose-2,6-bisphosphate content in affected canine erythrocytes was higher than normal. Studies of erythrocyte PFK isozymes revealed altered enzyme kinetic properties in affected dogs which appeared to be due to the loss of the M-type subunit.