Activity patterns of phosphofructokinase,glyceraldehydephosphate dehydrogenase,lactate dehydrogenase and malate dehydrogenase in microdissected fast and slow fibres from rabbit psoas and soleus muscle

Summary Methods for standardized determination of phosphofructokinase (PFK), glyceraldehydephosphate dehydrogenase (GAPDH), lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) activities in nanogram samples of microdissected single fibres of rabbit psoas and soleus muscle are described. Fast and slow fibres in soleus muscle show lower absolute activities of these enzymes than the respective fibre types in psoas muscle. Slow fibres represent a more uniform population in the two muscles according to absolute and relative activities of the enzymes investigated. Slow fibres are characterized by high activities of MDH and relatively low activities of glycolytic enzymes. Fast fibres in the soleus muscle represent a population with high activities of MDH and glycolytic enzymes. Fast fibres in psoas muscle represent a heterogeneous population with high activities of glycolytic enzymes and extremely variable activity of MDH. More than 10-fold differences exist in the MDH activities of the extreme types of this fibre population. Differences in the activity levels of MDH in single fast type fibres but also in the activities of glycolytic enzymes between fast and slow fibres are greater than those reported between extreme white and red rabbit muscles.     

Characterization of rabbit lactate dehydrogenase-M and lactate dehydrogenase-H cDNAs. Control of lactate dehydrogenase expression in rabbit muscle

Two cDNA clones were isolated, one corresponding to the mRNA coding for lactate dehydrogenase-M (LDH-M), the other to the mRNA coding for lactate dehydrogenase-H (LDH-H). The cDNA inserts consist of the entire open reading frame for LDH-M and a partial sequence, from amino acid 117 to 332, for LDH-H. Using these two clones as probes we demonstrate that: (a) the abundance of mRNA is muscle-type dependent; (b) the ratio M/H subunit for protein and mRNA is well related in the muscles studied; and (c) the M + H mRNA level is not relative to the total LDH activity.     

Perfusion of the psoas muscle of the rabbit. Metabolism of a homogeneous muscle composed of "fast glycolytic" fibres

A method was developed for the hemoglobin-free perfusion of the rabbit psoas muscle in situ. This muscle consists almost exclusively of fast-twitch (type IIb) glycolytic fibres and was therefore used as a model of a homogeneous muscle of the glycolytic, metabolic type.     

Aldolase and actin protect rabbit muscle lactate dehydrogenase from ascorbate inhibition

Muscle-type LDH (LDH-m4) activity is critical for efficient anaerobic glycolysis. The results here show that rabbit LDH-M4 is inhibited by concentrations of ascorbate normally found in tissues. Aldolase and muscle G-actin were found to protect and to reverse inhibitions of LDH-m4 by ascorbate. G-actins showed some species specificity. Myosin, tropomyosin and troponin from rabbit muscle and muscle proteins from other animal sources had no affect on the inhibitions by ascorbate. The substrate inhibition of LDH-m4 by pyruvate is partially relieved by the presence of aldolase and lowers the Km without affecting the Vm. G-actin under similar conditions has no affect. It is believed that these studies reflect some of the resting properties of glycolytic enzymes that bind and unbind to contractile elements. It is proposed that ascorbate facilitates the storage of glycogen in muscle at rest by inhibiting glycolysis.     

Relationship between myoglobin and succinate dehydrogenase in mouse soleus and plantaris muscle fibres

Summary This report describes a quantitative histochemical study of myoglobin in skeletal muscle fibres. The muscle fibres were classified as fast or slow on the basis of their quantitative myofibrillar ATPase histochemistry. A large range of myoglobin absorbance values was found among fast skeletal muscle fibres. This range was relatively small among slow fibres. The concentrations of myoglobin and the activities of succinate dehydrogenase in individual muscle fibres in serial sections are weakly correlated in both the mouse soleus and plantaris muscle. The myoglobin concentration is higher in fast and slow oxidative soleus muscle fibres and the succinate dehydrogenase activity in these fibres is lower than in oxidative plantaris muscle fibres in the same range of cross-sectional area.     

Autophosphorylation of glyceraldehydephosphate dehydrogenase and phosphorylation of protein from skeletal muscle microsomes

Glyceraldehydephosphate dehydrogenase purified from rabbit skeletal muscle is auto-phosphorylated with MgATP. Half-maximal phosphorylation is achieved around 0.3 mM. The phosphorylation is Ca2+ independent. The phosphoenzyme complex is labile in alkaline conditions and stable in moderately acid media. The complex is readily hydrolyzed by 0.1 M neutral hydroxylamine, indicating the complex formed is a high-energy acyl phosphate. The phosphorylation is reduced by nicotinamide adenine dinucleotides, reduced form (NADH), glyceraldehyde 3-phosphate, and nicotinamide adenine dinucleotide (NAD+). The enzyme is also dephosphorylated by these metabolites although to a lesser extent by NAD+. Calsequestrin isolated from rabbit skeletal muscle inhibits the phosphorylation of the enzyme. The phosphoenzyme behaves as a kinase catalyzing the phosphorylation of proteins of Mr 80 000 and 72 000 found in the skeletal muscle terminal cisternae/triad preparation. This reaction is enhanced by NADH. The phosphate found in the protein substrate has been shown to be the same phosphate initially involved in the phosphorylation of glyceraldehydephosphate dehydrogenase.     

The effects of pre- and perinatal undernutrition on the succinic dehydrogenase content of muscle fibres from fast and slow rat muscles

Summary Male rats were subjected to early undernutrition by limiting the mothers' food supply by 50% during pregnancy and lactation. At age 36 weeks, quantitative cytochemical determinations of succinic dehydrogenase activity were made in muscle fibres from the anterior tibialis and soleus muscles. Marked decreases were found in the former muscle but relatively little decrease was seen in the latter. This response of the muscles to early undernutrition was discussed with reference to other studies on pre and post-natal starvation.     

Effect of thyroidectomy on fast and slow muscle fibres of rat gastrocnemius muscle

A combined histochemical, biochemical and electrophoretic study with respect to the enzymes succnic dehydrogenase(SDH), myofibrillar adenosine triphosphatase (m-ATPase), lactate dehydrogenase (LDH) isozymes and myosin light chains was carried out to investigate the response of rat gastrocnemius muscle (medial head). Twelve weeks after thyroidectomy, the results indicated a shift from fast to slow type pattern of LDH isozymes, fibre type transformation from Type II to Type I and a decrease in SDH and m-ATPase activity. The results suggest, possible thyroidal involvement in determining the phenotypic properties of skeletal muscle.     

The number of satellite cells in slow and fast fibres from human vastus lateralis muscle

The aim of this investigation was to study the distribution of satellite cells in slow (type I fibres) and fast (type II fibres) fibres from human vastus lateralis muscle. This muscle is characterised by a mixed fibre type composition and is considered as the site of choice for biopsies in research work and for clinical diagnosis. Biopsy samples were obtained from five healthy young volunteers and a total of 1,747 type I fibres and 1,760 type II fibres were assessed. Satellite cells and fibre type composition were studied on serial muscle cross-sections stained with specific monoclonal antibodies. From a total of 218 satellite cells, 116 satellite cells were found in contact with type I fibres (53.6±8% of the satellite cells associated to type I fibres) and 102 satellite cells in contact with type II fibres (46.4±8% of the satellite cells associated to type II fibres). There was no significant difference (P=0.4) between the percentages of satellite cells in contact with type I and with type II fibres. Additionally, there was no relationship between the mean number of satellite cells per fibre and the mean cross-sectional area of muscle fibres. In conclusion, our results show that there is no fibre type-specific distribution of satellite cells in a human skeletal muscle with mixed fibre type composition.