Changes in serum creatine phosphokinase during submaximal exercise testing

The changes in creatine phosphokinase with exercise were studied in 70 subjects who had a submaximal exercise electrocardiogram carried out as part of their routine medical investigation. A significantly greater proportion of the subjects with a positive exercise ECG had a rise in CPK following exercise than did the subjects with a negative exercise ECG. The former had significantly lower initial CPK values, and this difference could be related to the different alteration of CPK with exercise in the two groups, for example by indicating a lower level of physical fitness in the group with positive exercise ECGs. However, the most likely explanation for the greater tendency of subjects with a positive exercise ECG to show a rise in CPK following exercise is greater CPK efflux from their ischemic myocardium.With refinements, measurement of CPK before and after exercise could be useful in helping to evaluate the diagnostic significance of the exercise ECG.     

Distribution and developmental transition of phosphoglycerate mutase and creatine phosphokinase isozymes in rat muscles of different fiber-type composition

Phosphoglycerate mutase and creatine phosphokinase have in mammals three isozymes (types MM, MB and BB) with similar tissue distribution and developmental transition in muscle cells. To assess whether the phenotype and the developmental switch of these isozymes differ in the diverse types of muscle fibers, the enzymatic activities and the isozyme patterns, analyzed by cellulose acetate electrophoresis, have been determined in rat soleus, extensor digitorum longus and gastrocnemius muscles during postnatal development. Both phosphoglycerate mutase and creatine phosphokinase activity increased in the three muscles, the increase in extensor digitorum longus and gastrocnemius being higher than in soleus. For the two enzymes the increase in activity was due to the progressive increment of the muscle-specific forms. It is concluded that whereas phosphoglycerate mutase and creatine phosphokinase type-B subunits are present at similar levels in both type I and type II muscle fibers, phosphoglycerate mutase and creatine phosphokinase type-M subunits exhibit much higher levels in type II fibers.     

Differentiation of actin-containing filaments during chick skeletal myogenesis.

Actin-containing filaments in cultures of differentiating chick skeletal muscle were examined by indirect immunofluorescence and transmission electron microscopy (TEM). As early as 20 h in culture, a large proportion of the pre-fusion population appeared as elongated, bipolar cells which contained actin filaments parallel to the longitudinal axis of the cell. During fusion, most of the mononucleated cells were bipolar and contained actin filament bundles which appeared to extend the entire length of the cell body and lie in close proximity to the plasma membrane. Striations were observed within actin filament bundles only after fusion had been completed. The small number of non-myogenic cells present in the cultures were not observed to display a bipolar morphology, orientation of actin fibers parallel to the longitudinal axis of the cell, or striations in their actin filament bundles.     

Monoclonal antibodies localize changes on myosin heavy chain isozymes during avian myogenesis

Monoclonal antibodies were used to identify and localize by immunoelectron microscopy epitopes on myosin isozymes. An antibody that reacts with an amino-terminal fragment of the myosin heavy chain maps on the myosin head 140 A distal to the head-rod junction. It identifies an epitope that is shared on adult and embryonic myosin, and detects two transitions in myosin expression during avian pectoralis myogenesis. Another antibody maps to the carboxyl terminus of the myosin rod. It is specific for an adult fast myosin epitope that is not detected in early developing pectoralis muscle. In contrast, an epitope that is present throughout development is identified by an antibody that reacts with a myosin light chain. This light chain epitope is localized at the head-rod junction. These results demonstrate structural changes in widely separated regions of the myosin molecule accompanying the sequential expression of developmental myosin isozymes.     

Inhibition of cardiac creatine phosphokinase by fluorodinitrobenzene

With electrophoretic evidence for a mitochondrial isoenzyme of creatine phosphokinase (CPK), we feel that functional studies are necessary to help further elucidate the properties of this isoenzyme. As one approach, fluorodinitrobenzene (FDNB) was used to examine its effect on mitochondrial CPK. In both polarographic studies and direct enzymatic studies, 10^?5 M FDNB was shown to almost completely inhibit the enzyme activity, as has been shown in skeletal muscle. In addition it was observed that the mitochondrial CPK was just as susceptible to the inhibitory effect of FDNB as the cytoplasmic isoenzyme.     

Accumulation of creatine kinase mRNA during myogenesis: molecular cloning of a B-creatine kinase cDNA

Cytosolic creatine kinase isoenzymes MM, MB, and BB are assembled from M or B subunits which occur in different relative amounts in specific tissues. The accumulation of mRNAs encoding the M and B subunits was measured during myogenesis in culture. The relative concentration of the two mRNAs was determined by hybridization with a M-CK cDNA probe isolated previously and a B-CK cDNA probe, the cloning and characterization of which is reported here. The B-CK cDNA hybridizes specifically to a 1.6-kb mRNA found in brain and gizzard but not in adult skeletal muscle tissue. The M-CK cDNA hybridizes to a smaller mRNA 1.4-kb long which is specific to skeletal muscle. In culture, the B-CK mRNA is transiently induced and then declines to a low but detectable level.     

Regulation of creatine phosphokinase expression during differentiation of BC3H1 cells

The intracellular mechanisms involved in the regulation of creatine phosphokinase expression in the BC3H1 muscle-like cell line have been examined under conditions of enzyme induction and repression. In the presence of low serum concentrations, BC3H1 cells cease to grow and synthesize high levels of creatine phosphokinase. When differentiated BC3H1 cultures are exposed to media containing high serum concentrations, cell division is reinitiated and further induction of creatine phosphokinase is inhibited. Accumulation of creatine phosphokinase-mRNA appears to be intimately coupled to the state of growth of BC3H1 cells. Log phase cells do not contain detectable levels of translatable creatine phosphokinase-mRNA; however, following cessation of growth, creatine phosphokinase-mRNA accumulates in approximate proportion to the increase in creatine phosphokinase activity. Reinitiation of cell division in quiescent differentiated cultures results in the arrest of further accumulation of creatine phosphokinase-mRNA but does not inhibit the translation of pre-existing creatine phosphokinase-mRNA. Under conditions of enzyme repression, however, the newly synthesized creatine phosphokinase appears to be enzymatically inactive. These results indicate that the expression of the muscle phenotype in BC3H1 cells is regulated by components present in serum and that myogenic differentiation is at least partially reversible following re-entry of quiescent cells into the cell cycle.     

Damage to the creatine phosphokinase of rat brain synaptosomes during molecular oxygen activation

It was shown that activation of molecular oxygen by Fe2+ ascorbate causes damage to creatine phosphokinase of rat brain synaptosomes. The creatine phosphokinase inactivation did not correlate with activation of lipid peroxidation in synaptosomes. The enzyme damage was the result of direct interaction with active oxygen species.     

Pyruvate kinase and creatine phosphokinase during development of the chicken with muscular dystrophy

Pyruvate kinase and creatine phosphokinase activities in breast muscle extracts and in serum, and protein content of the muscle extracts were determined during the first eight weeks of development of control and dystrophic chickens. In the dystrophic chicken serum enzyme levels were significantly greater than, and muscle protein content and enzyme activities on a gram wet weight basis were significantly less than control values, by the second week after hatching and thereafter. For both muscle and serum the relative differences between control and dystrophic groups was greater for pyruvate kinase than crearine phosphokinase. On a specific activity basis only pyruvate kinase levels in dystrophic muscle were significantly less than control values in 2–8-week-old chickens.     

Intimate coupling of creatine phosphokinase and myofibrillar adenosinetriphosphatase

ATPase and creatine phosphokinase (CPK) activities of isolated cardiac myofibrils were determined with ³²P γ-labeled ATP alone and with the addition of phosphorylcreatine (PC). With ATP and PC as substrates the label in the inorganic phosphate formed is greatly diluted indicating that the ATP formed by PC through CPK can reach the ATPase active site more readily than labeled ATP from the medium. The tight coupling of the ATPase and CPK activities further strengthens our view that PC serves an important role as high energy carrier between the energy producing sites (mitochondria) and the energy utilizing sites (myofibrils).     

The effect of anthracyclines on heart mitochondria respiration during the action of creatine phosphokinase

It was shown that during glutamate+malate oxidation in the presence of creatine, antitumour anthracycline antibiotics strongly inhibit the rate of oxygen uptake by rat heart mitochondria; ADP excess activated the respiration up to the initial level, i.e., that observed after the first addition of ADP. Carboxyatractyloside addition to a system containing creatine (or hexokinase+glucose) results in the stimulation of rubomycin-induced mitochondrial respiration. Substitution of carboxyatractyloside by oligomycin gives very similar results. It is supposed that anthracycline antibiotics exert a manyfold effect on heart mitochondrial membranes which results in impaired compartmentation of enzymatic systems providing for oxidative phosphorylation.     

Lactate dehydrogenase isozymes: Qualitative and quantitative changes during primate evolution

Qualitative differences in primate lactate dehydrogenase (LDH) were investigated using starch gel electrophoresis. Three types of mutation were observed: (1) variability in LDH-1, reflected in the intermediate bands, occurring at the species level; (2) variation in LDH-5 reflected in the intermediate bands, occurring at the infraorder level; (3) a variation affecting mobility of the intermediate bands only, not that of LDH-1 or LDH-5. This type of variation occurred several times, probably at the genus level. Between Pan and Homo it was ascertained to be an LDH-5 variation. Quantitative differences in the relative amounts of the B and A subunits were studied by determining the density of bands using a Densicord densitometer. In a series of primate erythrocytes, a progressive increase of B/A ratio took place as the evolutionary scale was ascended. Comparison of homologous tissues of Perodicticus potto and Saimiri sciurea revealed that all tissues, with the exception of liver, exhibited an increase in the B/A ratio.This investigation was supported in part by contract AF 29(600)-5587 and NSF grant GB-7426.