Red cell glycolysis in the myodystrophic child

Study on the erythrocytes from myotonic dystrophy with multi-nuclear NMR

We have studied the water permeability through membranes, the function of the Na pump, and glucose metabolism of erythrocytes of patients with myotonic muscular dystrophy (MyD) using 1H--, 23Na, and 13C-NMR techniques. A significant decrease in water permeability was recognized in the MyD erythrocyte membrane, and impaired Na pumping was suspected to be correlated with the former biochemical abnormalities in band III protein of MyD erythrocyte membrane. Significant acceleration of glycolysis in the erythrocyte for the first 160 minutes was also recognized in MyD; however, the production of lactate showed no difference between MyD and controls. The increased glucose uptake in MyD may be compensatory to the diminished pumping mechanism, but further information, such as inorganic phosphate permeability and the activity of the rate-limiting enzyme of erythrocyte glycolysis, is needed.

Decreased osmotic fragility in heritable canine myopathy

Osmotic fragility was examined in red blood cells from dogs with a heritable muscle disorder that clinically resembles a muscular dystrophy. Several erythrocyte abnormalities have been reported in patients with certain forms of muscular dystrophy and it is thought that these changes reflect genetically induced alterations in the plasma membrane. It is believed that the examination of erythrocytes may eventually lead to the understanding of membrane involvement in muscle disorders. In this study, the mean osmotic fragility was found to be significantly lower in affected cells than in normal cells. These differences were maintained regardless of changes in incubation temperature (5 degrees, 20 degrees, or 35 degrees C) and pH (6.5, 7.0, 7.5, or 8.0). Quantitative analysis of glycolytic metabolites and adenine nucleotide concentrations revealed little variance between erythrocytes from normal and affected animals. Similarly, the pattern of membrane protein phosphorylation in intact erythrocytes from affected animals did not differ from that observed when erythrocytes from normal animals were examined. Of the red cell indices measured, the erythrocyte count in affected animals was moderately increased, but both the mean corpuscular volume and mean corpuscular hemoglobin content were significantly reduced. From these data it is concluded that the decrease in osmotic fragility cannot be explained by differences in cell metabolism or energy production. However, the decrease in affected cell mean corpuscular volume and mean corpuscular hemoglobin content may be correlated with the decrease in osmotic fragility in a manner similar to that observed in the hemolytic disorder of beta-thalassemia.

Altered erythrocyte spectrin extractability in Duchenne muscular dystrophy

Spectrin extractability was measured in the erythrocyte membranes obtained from patients with Duchenne muscular dystrophy (DMD) and normal matched controls. After the extraction of spectrin by adding deionized water, an aliquot of the pellet was applied to 6% SDS-polyacrylamide gels. Spectrin-Band 3 ratio on the gels was used as an indicator of spectrin extractability. Our data disclosed that spectrin extractability is significantly reduced in DMD patients when compared with that of controls and these results suggest that spectrin from DMD patients is more tightly bound to the membranes. Our data may also be applicable to the discussion of the relationship of spectrin to other membrane properties as well as to previously described membrane abnormalities in DMD erythrocytes.

Biochemistry of muscle membranes in Duchenne muscular dystrophy

In Duchenne muscular dystrophy, as in other genetic diseases, there must be a biochemical abnormality. This fundamental genetic fault has not been identified, but several indirect lines of evidence suggest that the surface membranes of skeletal muscle are affected. The biochemical evidence implies abnormal egress of soluble enzymes and other proteins from muscle, abnormal permeability, and altered properties of membrane-bound enzymes. As a result of the presumed genetic abnormality, functional properties are altered, and impaired regulation of intracellular calcium content could be responsible for the hallmarks of the disease--progressive weakness and degeneration of muscle. The evidence is by no means conclusive, however, and some of it is contradictory. Technical advances must be made before isolated membranes can be characterized biochemically. Other theories are also being evaluated.

Erythrocyte glucose metabolism in Duchenne muscular dystrophy

We compared glucose metabolism by erythrocytes from patients with Duchenne muscular dystrophy and by erythrocytes from control individuals. There was a significant decrease in the rate of lactate production at pH 7.2 in the dystrophic group. When the pH of the incubation medium was changed to 8.0, we found that the increase in the rate of lactate production for the dystrophic group was significantly larger. We measured the concentrations of key glycolytic metabolites and adenine nucleotides and determined the values of the energy charge during these incubations. We also determined the concentrations of polyol pathway intermediates, the activities of the oxidative portion of the pentose phosphate pathway and the activities and kinetics of phosphofructokinase from both cell groups. There were no significant differences between groups for any of these variables.

Hypoxanthine-guanine phosphoribosyltransferase activity of blood and muscle in Duchenne dystrophy

Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity was measured in red cells and in skeletal muscles of normal and Duchenne subjects. [8-14C] hypoxanthine was used as substrate, and 5-phospho-alpha-D-ribose 1-diphosphate (PRPP) was used as the ribose-5-phosphate donor. The [8-14C] inosine monophosphate (IMP) formed was separated by high-voltage electrophoresis, and radioactivity was measured by lipid scintillation counting. HGPRT activity in Duchenne and normal red-cell hemolysates was similar, but such activity was significantly higher in Duchenne than in normal muscle homogenates. Red cells of both normal and Duchenne subjects had significantly higher enzyme activity than did skeletal muscles. It is suggested that increased HGPRT activity may be involved in enhancing protein synthesis by increasing intracellular levels of purine ribonucleotides.

Role of intracellular calcium in promoting muscle damage: a strategy for controlling the dystrophic condition

It is suggested that various muscle diseases and examples of experimentally-induced muscle damage arise because of a high calcium level in the myoplasm. When [Ca2+]i is raised experimentally in amphibian or mammaliam muscle by treatment with A23187 or caffeine, myofilament degradation follows quickly. Such a rapid action suggests the involvement of a sequence of proteolytic activity that is stimulated by a rise in [Ca2+]i. Ca2+ might either trigger protease activity directly or indirectly, or promote the release of lysosomal enzymes. A high [Ca2+]i in dystrophic muscle is believed to be the resultant of a sequence of events that is summarized in the figure. Suggestions are presented for different ways in which the steady-state position of [Ca2+]i might ultimately be controlled for the clinical amelioration of some dystrophic conditions.

The sodium pump of erythrocytes from patients with Duchenne muscular dystrophy: effect of ouabain on the active sodium flux and on (Na+, K+)ATPase

Active ion exchanges across erythrocyte membrane from patients with Duchenne muscular dystrophy were studied by two methods: --erythrocyte ghosts (Na+,K+)ATPase activity and its sensibility to ouabain, using an enzymatic method; --active sodium outflux and its sensibility to ouabain using a radioisotopic method. (Na+,K+)ATPase activity and active sodium outflux were decreased in dystrophic patients compared to normal sex- and age-matched controls. Enzymatic activity and active sodium outflux were inhibited by ouabain 10(-4) M in patients and in controls. Inhibition of the active sodium outflux was lower in patients than in controls. The results are discussed in light of the literature.

Erythrocyte ghost (Na+ + K+) ATPase activity in mice with hereditary muscular dystrophy (strain C57 BL/64J/dy)

Erythrocyte ghost (Na+ + K+) ATPase activity was studied in mice with hereditary muscular dystrophy (strain C 57 BL 6J/dy) and appropriate controls. No difference was observed in the enzymatic activity between dystrophic and any of the healthy genotypes. Ouabain 5 mM and 0.1 mM inhibited the enzymatic activity and no difference was observed between dystrophic and control animals. The results are discussed in the light of the literature.

Effect of ouabain upon erythrocyte membrane adenosine triphosphatase in Duchenne muscular dystrophy

The adenosine triphosphatase activity of erythrocyte ghosts from patients with Duchenne muscular dystrophy was inhibited by 10(-4) M ouabain to a smaller extent than in normals, when measured in the presence of either high or low concentrations of sodium or potassium ions. The inhibition by ouabain of the enzyme in normal ghosts, measured with low sodium or potassium ions, was less if the erythrocytes were first incubated with plasma from Duchenne patients than if incubated with normal plasma. Similar results were obtained when the ghosts themselves were incubated with Duchenne or normal plasma before assay.

5'-AMP aminohydrolase activity in erythrocytes from normal and dystrophic individuals

5'-AMP aminohydrolase activities in red blood cells from normal human adults and from patients with pseudohypertrophic dystrophy, myotonic dystrophy, limb girdle dystrophy, neuromuscular atrophy, Charcot-Marie Tooth Disease, and spinal muscular atrophy were examined. In contrast to the greatly decreased skeletal muscular levels of 5'-AMP aminohydrolase observed in Pseudohypertrophic muscular dystrophy, levels in red blood cells of all patients were not significantly different from normals. Pyruvate kinase and creatine kinase activities were determined for comparative purposes. The density distribution of normal and dystrophic erythrocytes were essentially identical.