Table 2.
Summary of muscle characteristics studied in two patients with chronic obstructive pulmonary disease, techniques employed and properties assessed
| Characteristic |
Patients |
Technique | Properties | |
|---|---|---|---|---|
| COPD #1 | COPD #2 | |||
| Fiber types | ||||
| Distribution | * | * | Myofibrillar ATPase28,29 | Fiber Types (%) |
| Size | * | * | Digitizing tablet53 | Cross sectional area (μm2) |
| Capillarization | * | * | Lectin technique30 | Number of capillaries (CC) |
| Oxidative potential | * | * | Microphotometry31 | SDH activity (Vmax) |
| Cation transport | * | * | Microphotometry32,33 | Ca2+-ATPase activity (Vmax) |
| Metabolic pathways (Vmax) | ||||
| CS, SDH, MDH | * | Fluorometric35,36 | Citric acid cycle | |
| COX | * | Spectrophotometric18 | Electron transport system | |
| HADH | * | Fluorometric35,36 | Fat oxidation | |
| HEX | * | Fluorometric35,36 | Glucose oxidation | |
| PHOSPH | * | Fluorometric35,36 | Glycogenolysis | |
| PFK, PK, LDH | * | Fluorometric35,36 | Glycolysis | |
| CPK | * | Fluorometric35,36 | High-energy phosphate transfer | |
| Metabolic status (Concentration) | ||||
| ATP, ADP, AMP, IMP,TAN | * | * | HPLC38 | Energy charge |
| PCr, Cr,TCr | * | * | Fluorometry21 | Energy charge |
| Pyruvate, lactate | * | * | Fluorometry21 | Glycolytic metabolites |
| Glycogen | * | * | Fluorometry21 | Carbohydrate substrate |
| Transporters (Content) | ||||
| GLUT1, GLUT4 | * | * | Electrophoresis/Western blotting39 | Glucose transport |
| MCT1, MCT4 | * | * | Electrophoresis/Western blotting39 | Lactate transport |
| Cation transport | ||||
| Na+ -K+-ATPase | ||||
| Vmax | * | * | Spectrophotometric (3–0-MFPase)40,41 | Maximal activity |
| Content | * | * | Scintillation (3H-Ouabain binding)42 | Enzyme content |
| Ca2+-ATPase (SR) | ||||
| Vmax, Ca50, ηH | * | Spectrophotometric44,45 | Maximal activity; Ca2+-sensitivity | |
| Ca2+-uptake | * | Spectrophotometric44,45 | Ca2+-uptake | |
| Ca2+-release | * | Spectrophotometric44,45 | Ca2+-release | |
Notes: The characteristics assessed included both the processes involved in the production of energy and the utilization of energy by the muscle cell. Metabolic status is a measure of the energetic state of the cell as assessed by the high-energy phosphate compounds. Metabolic pathway potential is based on the maximal activity (Vmax) of representative enzymes. For the transporter potential, the content of two isoforms of glucose and lactate were measured. For cation transport, the maximal activity (Vmax) of both the enzymes involved in sarcolemma and t-tubule transport of Na+/K+ was measured (Na+-K+-ATPase) as well as the sarcoplasmic reticulum (SR) Ca2+-uptake (Ca2+-ATPase). The SR Ca2+-ATPase was also supplemented by measures of Ca2+-release and Ca2+-uptake. Selected fiber type characteristics were assessed by histochemistry. See Methods for further details.
Abbreviations: CS, citrate synthase; SDH, succinic dehydrogenase; MDH, malate dehydrogenase; COX, cytochrome c oxidase; HADH-3, hydroxyacyl-CoA dehydrogenase; HEX, hexokinase; PHOSPH, phosphorylase; PFK, phosphofructokinase; PK, pyruvate kinase; LDH, lactate dehydrogenase; CPK, creatine phosphokinase; ATP, adenosine triphosphate; ADP, adenosine diphosphate; AMP, adenosine monophosphate; IMP, inosine monophosphate; TAN, total adenine nucleotide; PCr, phosphocreatine; Cr, creatine; TCr, total creatine; GLUT1, glucose transporter isoform 1; GLUT4, glucose transporter isoform 4; MCT1, monocarboxylate transporter isoform 1; MCT4, monocarboxylate transporter 4; Ca50, calcium concentration necessary to elicit 50% Vmax; nH, Hill coefficient obtained by using the relationship between Ca2+ concentration and Ca2+-ATPase activity; SR, sarcoplasmic reticulum.