Parvalbumin reduction in relation to possible perturbations of Ca2+-homeostasis in muscular dystrophy.
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Animals↗
Biomedical subjects
D Pette
Publications and source records attributed to D Pette.
Biochemical and ultrastructural changes of skeletal muscle mitochondria after chronic electrical stimulation in rabbits.
The purpose of the present investigation was to follow and correlate changes of structural and biochemical markers of energy metabolism during chronic electrical stimulation of tibialis anterior muscle in rabbits. In the superficial portion of the muscle, 5 to 6-fold increases occurred in enzyme activities of the citric acid cycle and of fatty acid oxidation after 28 days of stimulation. Enzyme activity changes in the deep, more oxidative part of the muscle were relatively smaller. Consequently, levels of the citric acid cycle enzymes became similar in superficial and deep parts of the muscle after the longest stimulation periods. With the exception of hexokinase, which increased in parallel with the citric acid cycle enzymes, glycolytic enzymes decreased 2 to 3-fold. Muscle mass and fibre size remained unchanged, while capillary density and capillary to fiber ratio increased 2-fold. The volume density of total mitochondria increased in a fashion similar to the changes of the enzymes of the citric acid cycle (7-fold in superficial and 3.5-fold in deep parts of the muscle) and, thus, approached values found in heart muscle. Disproportionate changes in enzyme activities of ketone body utilisation and of mitochondrial glycerolphosphate oxidase indicated qualitative changes within the mitochondrial population. However, the proportion of subsarcolemmal to interfibrillar mitochondria, as well as the area of inner mitochondrial membrane per unit volume of mitochondrion remained unchanged. Similarly, intracellular lipid deposits remained unchanged with stimulation. It is concluded that there is an excellent agreement between morphometric and biochemical measurements of tissue oxidative capacity.
Animals↗
Metabolic heterogeneity of muscle fibres.
Mammalian skeletal muscle is an extremely heterogeneous tissue. Its diversity results from a spectrum of fibres which are metabolically suited to a wide range of functional demands. As judged from enzyme activity analyses of single fibres, the metabolic properties of fibres belonging to the same motor unit are similar or identical. It is likely, therefore, that the phenotype expression of muscle fibres is primarily under neural control. Differences in recruitment patterns of various motor units explain the wide range of metabolic properties as evidenced by pronounced variations in enzyme activities and enzyme activity ratios. There exist large overlaps between the activity spectra of various enzymes of anaerobic and aerobic metabolism in slow- and fast-twitch fibres. Nevertheless, these two major fibre classes can be distinguished by discriminative enzyme activity ratios (e.g. phosphofructokinase/malate dehydrogenase, phosphofructokinase/3-hydroxyacyl-CoA dehydrogenase, fructose-1,6-diphosphatase/phosphofructokinase). Moreover, slow-twitch fibres display an H-type isozyme pattern of lactate dehydrogenase, whereas fast-twitch fibres are characterized by a predominance of LDH-5. No clear-cut differences exist between enzyme activity profiles and LDH isozyme patterns of the IIA and IIB subgroups of fast-twitch fibres. Comparative studies indicate that the metabolic properties of IIA and IIB fibres vary in different animal species. This observation supports the notion that metabolic and myosin-related properties of muscle fibres may be regulated independently. Due to relatively high turnover rates of enzymes of energy metabolism in muscle, changes in functional demands may be met by relatively rapid changes in metabolic properties. In view of these findings it is not surprising that muscle fibres display a spectrum of metabolic properties and represent stages within a dynamic equilibrium.
Animals↗
Prostaglandins and cyclic AMP stimulate creatine kinase synthesis but not fusion in cultured embryonic chick muscle cells.
Cyclic AMP levels have been measured in cultures derived from 12-day-old chick embryonic muscle. A rise in concentration was found after the onset of myoblast fusion. Cells cultured at a medium Ca2+ concentration of 0.1 microM did not fuse and exhibited only a small rise in cyclic AMP concentration during culture. Addition of 1.4 mM Ca2+ to these cells after 50 h in culture caused rapid, synchronous fusion with a concomitant rise in cyclic AMP levels. Indomethacin, an inhibitor of prostaglandin synthesis, did not inhibit fusion, but inhibited the rise in cyclic AMP concentration. Indomethacin-treated cultures exhibited lower creatine kinase levels, though no change in the ratio of the three isoenzymes was observed. Addition of prostaglandins E1 and E2 to indomethacin-treated cultures overcame this inhibition. We propose that prostaglandin synthesis is a consequence of the stimulation of myoblast fusion and that via cyclic AMP it stimulates protein synthesis.
Alprostadil↗
Myoblast fusion and inositol phospholipid breakdown: causal relationship or coincidence?
The fusion of embryonic chick myoblasts has been examined in culture. Cells were prepared from 12-day-old chick embryonic breast muscle and cultured for 50 h at a Ca2+ concentration in the medium of 10(-7) M. During this period they attain fusion competence. Addition of 1.4 mM-Ca2+ to these cells elicits rapid fusion. Changes in the metabolism of myoblast phospholipids in response to the raised Ca2+ concentration have been examined. Only the inositol phospholipids are affected. Phosphatidylinositol, phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate are rapidly broken down and 1,2-diacylglycerol and phosphatidic acid are synthesized. Myoblast fusion has also been found to be stimulated by a factor present in chick embryo extract, probably of neuronal origin. A receptor-mediated mechanism for myoblast fusion is proposed. This envisages the polyphosphoinositides acting as a fusion block, either themselves or by their binding to membrane proteins. The inositol phospholipid breakdown could result in a more fluid membrane and the breakdown products 1,2-diacylglycerol and phosphatidic acid, two known fusogens, could stimulate fusion.
Animals↗
Enzyme activities and activity profiles in muscle fibers of dystrophic, immature-normal, and adult-normal BL6 mice.
Enzyme activities of energy metabolism were determined in both homogenates and single fibers of immature-normal (IN), adult-normal (AN), and adult-dystrophic (AD) tibialis anterior (TA) muscle of BL6 mice. Mitochondrial enzyme activities were similar in AN and AD, whereas lower activities were found in IN. Creatine kinase, glycogenolytic, and glycolytic enzyme activities were reduced but glucose 6-phosphate dehydrogenase was elevated in AD and IN as compared to AN. IN and AD both showed an increase in the H-subunit of lactate dehydrogenase. Microphotometric measurements of succinate dehydrogenase (SDH) revealed large fiber differences in AN whereas smaller scattering was observed both in IN and AD. Although similarities exist between enzyme and isozyme patterns of anaerobic metabolism in AD and IN, this does not hold for mitochondrial enzymes.
Animals↗
Inter- and intraspecies comparisons of fibre type distribution and of succinate dehydrogenase activity in type I, IIA and IIB fibres of mammalian diaphragms.
Fibre types in the costal region of the diaphragm muscle of several mammalian species with widely different respiratory rates were examined microphotometrically for succinate dehydrogenase (SDH) activity. Mean activities indicated no significant (p greater than 0.05) difference between the type I and IIA fibres for any of the species examined. SDH activities in type IIB fibres were significantly lower (p less than 0.05) than either the type I or type IIA fibres in the cat, guinea pig, rat and rabbit whereas in the mouse no difference was found. The dog had no classical type 1B fibres. Analysis of the distribution of SDH activities by fibre type indicated a wide scattering of scores with no distinct separation between fibre types. Large differences in SDH activity were noted between species. Mean SDH activities were highest in the mouse and rat, intermediate in the rabbit and guinea pig and lowest in the cat and dog. These data suggest an association between respiratory rate and aerobic oxidative potential of the various fibre types in diaphragms of the species examined.
Animals↗
pH lability of myosin ATPase activity permits discrimination of different muscle fibre types in crustaceans.
Myofibrillar actomyosin ATPase activity has been studied histochemically in the closer muscle of the crab Eriphia spinifrons. Preincubation at pH 4.6 and 5.0 reveals differences in the lability of the ATPase. This permits the discrimination of four fibre types. Of these, three represent subgroups of rapidly contracting fibres. The histochemically defined fibre types correspond well with four groups defined according to electrophysiological criteria.
Actomyosin↗
Microphotometric determination of enzyme activities in type-grouped fibres of reinnervated rat muscle.
Activities of succinate dehydrogenase (SDH), glycerolphosphate oxidase (GP-OX), cytochrome oxidase (CYT-OX) and lactate dehydrogenase (LDH) were determined microphotometrically in single, actomyosin-ATPase typed ( Guth and Samaha 1970) fibres within cross-sections of normal and reinnervated rat tibialis anterior muscles. SDH and GP-OX activities displayed pronounced scattering and large overlaps existed between alpha-, alpha beta-, and beta-fibres of normal muscle. Coefficients of variation were in the range of 16-40% for GP-OX and SDH in the different fibre populations. Enzyme activity determinations in type-grouped alpha-, alpha beta-, and beta-fibres of reinnervated muscle showed much less scattering than in normally distributed alpha-, alpha beta-, and beta-fibres of control muscles. Coefficients of variation were in the range of 10-13% for SDH, GP-OX, CYT-OX and LDH. The experimental error of the kinetic microphotometric measurement of enzyme activities in situ is in the range of 10% ( Reichmann and Pette 1982). Our results therefore suggest a high degree of metabolic similarity or homogeneity of typed-grouped muscle fibres and thus support the assumption that type-grouped fibres are homogeneous and correspond to regularly assembled motor units.
Actomyosin↗
Glycerolphosphate oxidase and succinate dehydrogenase activities in IIA and IIB fibres of mouse and rabbit tibialis anterior muscles.
Quantitative microphotometric measurements of two mitochondrial flavoproteins, glycerolphosphate oxidase (GP-OX) and succinate dehydrogenase (SDH), were performed on serial sections of mouse and rabbit tibialis anterior (TA) muscles in order to study the distribution of these two enzymes and their activity ratios in IIA and IIB fibres. The measurements showed a large scatter of the two enzyme activities in these two myosin-based fibre types. In rabbit TA, IIA and IIB fibres have similar GP-OX activities, whereas generally IIA fibres have higher SDH activities than IIB fibres. An inverse distribution of the two enzymes exists in mouse muscle. Generally, IIA fibres of mouse TA display low SDH and IIB fibres high SDH activities. The mean activity of GP-OX is slightly higher in IIA than in IIB fibres of mouse TA. Since measurements of both enzymes were taken in the same fibres, the ratio of their activities in each fibre could be evaluated. The SDH/GP-OX activity ratios vary significantly between the two fibre populations both in rabbit and in mouse. The ratio is high in IIA and low in IIB fibres of rabbit TA, whereas it is low in IIA and high in IIB fibres of mouse TA.
Adenosine Triphosphatases↗
Lactate dehydrogenase isozymes in type I, IIA and IIB fibres of rabbit skeletal muscles.
Lactate dehydrogenase (LDH) isozyme patterns were analyzed by polyacrylamide (PAA) slab gel electrophoresis in extracts prepared from various rabbit skeletal muscles of defined fibre composition and by PAA microelectrophoresis of microdissected, histochemically typed single muscle fibres. The results obtained by electrophoresis of whole muscle extracts generally agreed with the data obtained from single fibre electrophoresis, i.e. the LDH isozyme pattern corresponded to that of the predominant fibre type. Type I fibres from soleus and semitendinosus muscles were characterized by a unique pattern of all 5 LDH isozymes with a predominance of LDH-1, 2 and 3. The major fraction (80%) of the type II fibres from extensor digitorum longus and tibialis anterior muscles contained only LDH-5 (M4). About 20% of the type II fibres contained in addition to LDH-5 small amounts of LDH-4 and LDH-3. The fraction of fibres containing LDH-5, LDH-4, and LDH-3 was similar (ca. 20%) in the histochemically defined IIA and IIB subpopulations. In view of the fact that the major fractions of rabbit IIB fibres display low and of IIA fibres high aerobic oxidative capacities ( Reichmann and Pette 1982), these data indicate that the expression of the H-subunit of LDH is not correlated with the aerobic-oxidative capacity of the fibre. It also appears not to be correlated with the presence of different myosin isoforms in IIA and IIB fibres.
Animals↗
Effects of different patterns of long-term stimulation on blood flow, fuel uptake and enzyme activities in rabbit fast skeletal muscles.
Long-term electrical stimulation (14-28 days) of rabbit fast muscles (tibialis anterior, TA and extensor digitorum longus, EDL) using intermittent high frequency (3 trains per min of 5 s duration at 40 Hz, for 8 h per day) produced changes in enzyme activities similar to those found with continuous stimulation at a frequency occurring in nerves to slow muscles (10 Hz). The activity of citrate synthetase, 3-hydroxyacyl-CoA dehydrogenase and succinate dehydrogenase increased two to 3-fold within 28 days. There was a 4-fold increase in hexokinase whereas phosphofructokinase, pyruvate kinase, lactate dehydrogenase and fructose-1,6-diphosphatase decreased to about 60% of the activity levels in the contralateral unstimulated muscles. Blood flow and oxygen consumption at rest were not changed even after 28 days of stimulation, but were increased during contractions in muscles stimulated at either frequency, the level being twice as high as in control muscles. Glucose uptake was similar to that in control muscles both at rest and during contractions and the output of lactate was similar to that found in control muscles in muscles stimulated at 40 Hz. Muscles stimulated at 10 Hz had smaller lactate output. Thus intermittent stimulation at high frequency (40 Hz) and continuous low frequency (10 Hz) produced similar changes in aerobic metabolism and fuel uptake provided that the total number of stimuli was comparable and that the stimulation was carried out for sufficiently long period.
Animals↗
Exercise-induced fibre type transitions with regard to myosin, parvalbumin, and sarcoplasmic reticulum in muscles of the rat.
Effects of a long-term, high intensity training program upon histochemically assessed myofibrillar actomyosin ATPase, myosin composition, peptide pattern of sarcoplasmic reticulum (SR), and parvalbumin content were analysed in muscles from the same rats which were used in a previous study (Green et al. 1983). Following 15 weeks of extreme training, an increase in type I and type II A fibres and a decrease in type II B fibres occurred both in plantaris and extensor digitorum longus (EDL) muscles. In the deep portion of vastus lateralis (VLD), there was a pronounced increase from 10 +/- 5% to 27 +/- 11% in type I fibres. No type I fibres were detected in the superficial portion of vastus lateralis (VLS) both in control and trained animals. An increase in slow type myosin light chains accompanied the histochemically observed fibre type transition in VLD. Changes in the peptide pattern of SR occurred both in VLS and VLD and suggested a complete transition from type II B to II A in VLS and from type II A to I in VLD. A complete type II A to I transition in the VLD was also suggested by the failure to detect parvalbumin in this muscle after 15 weeks of training. Changes in parvalbumin content and SR tended to precede the transitions in the myosin light chains. Obviously, high intensity endurance training is capable of transforming specific characteristics of muscle fibres beyond the commonly observed changes in the enzyme activity pattern of energy metabolism. The time courses of the various changes which are similar to those in chronic nerve stimulation experiments, indicate that various functional systems of the muscle fibre do not change simultaneously.
Adenosine Triphosphatases↗
Effects of chronic stimulation on the metabolic heterogeneity of the fibre population in rabbit tibialis anterior muscle.
Chronic indirect stimulation (10 Hz) was performed on rabbit tibialis anterior muscle. Long-term stimulation (52-140 days) produced a transformation of the fast tibialis anterior into a slow red muscle as judged from the histochemistry of myofibrillar actomyosin ATPase, the pattern of myosin light chains and the thorough rearrangement of the enzyme activity pattern of energy metabolism. Activity levels of citrate synthetase (CS), malate dehydrogenase (MDH), succinate dehydrogenase (SDH), 3-hydroxy-acyl-CoA dehydrogenase (HAD), and lactate dehydrogenase (LDH) were determined quantitatively by either microbiochemical assays (CS, MDH, HAD and LDH) on microdissected, single fibres or by kinetic microphotometry on cross-sectioned fibres (SDH). The activity profiles of these enzymes displayed pronounced scattering in the fibre population of the unstimulated muscle. Despite a several fold increase in the activities of CS, MDH, SDH and HAD and a pronounced decrease in LDH, chronic stimulation failed to abolish the metabolic heterogeneity of the fibre population. It is possible that chronic indirect stimulation cannot produce uniformity of fibres because of continuing diverse natural activity of the motor units.
3-Hydroxyacyl CoA Dehydrogenases↗
J.B. Wolffe memorial lecture. Activity-induced fast to slow transitions in mammalian muscle.
Chronically increased contractile activity by low-frequency stimulation induces a transformation of fast- into slow-twitch muscle fibers in the rabbit. This transformation is progressive with the duration of the stimulation and affects various functional systems of the muscle fiber in an orderly sequence. Early changes in enzyme activities and isozymes of energy metabolism result in a "white to red" metabolic transformation. Simultaneously, cytosolic Ca2+-binding and Ca2+-sequestration are reduced by a decrease in parvalbumin and a transformation of the sarcoplasmic reticulum membranes. The fast to slow transformation is completed by an exchange of fast with slow-type myosin isoforms. Changes in total RNA and qualitative and quantitative alterations in translatable mRNA indicate that the various transitions result from altered translational and transcriptional activities. The qualitative similarity of changes evoked by long-term endurance training suggest that fast to slow transitions represent a regular response to increased contractile activity. The specific time courses at which various functional systems of the fiber respond, point to the existence of different thresholds. These differences increase the adaptability of the fiber by changing its properties in a graded fashion. The phenotype of a muscle fiber appears thus to be dynamic and is modified according to the actual functional demand.
Animals↗
The ratio between intrinsic 115 kDa and 30 kDa peptides as a marker of fibre type-specific sarcoplasmic reticulum in mammalian muscles.
Sarcoplasmic reticulum displays characteristic differences in Ca2+-uptake, Ca2+-ATPase and the pattern of membrane proteins in type I, IIA and IIB fibres. The ratio between the 115 kDa Ca2+-ATPase and a 30 kDa protein is of characteristic magnitude in the sarcoplasmic reticulum of the three fibre types in rat muscles. The slow-to-fast fibre type transformation observed in rabbits during chronic nerve stimulation is accompanied by predictable changes of this ratio.
Animals↗
Coordinate expression of alkali and DTNB myosin light chains during transformation of rabbit fast muscle by chronic stimulation.
Chronic nerve stimulation induces an almost complete exchange of the fast myosin light chains (LC) LC1f and LC2f to the slow light chains LC1s and LC2s. LC3f decreases only by 30%. The exchange of the DTNB LCs (LC2f to LC2s) precedes that of LC1f to LC1s. However, the equimolar ratio of total alkali to total DTNB LCs is maintained. This points to a hitherto unknown regulation that preserves this ratio independent of whether alkali and DTNB LCs are expressed in fast or slow isotypes.
Alkalies↗
Rapid reduction in parvalbumin concentration during chronic stimulation of rabbit fast twitch muscle.
Chronic indirect stimulation of fast twitch rabbit muscle induced a rapid reduction in parvalbumin concentration. When compared to the unstimulated contralateral muscle, parvalbumins were reduced to 55% following 6 days of stimulation. Prolonged stimulation further reduced parvalbumins so that they were undetectable after 28 days. The time course of these changes appears to be related with the previously observed changes in the sarcoplasmic reticulum.
Animals↗