phosphocreatine and Hypertrophy

Skeletal muscle tissue is sensitive to the acute and chronic stresses associated with resistance training. These responses are influenced by the structure of resistance activity (i.e. frequency, load and recovery) as well as the training history of the individuals involved. There are histochemical and biochemical data which suggest that resistance training alters the expression of myosin heavy chains (MHCs). Specifically, chronic exposure to bodybuilding and power lifting type activity produces shifts towards the MHC I and IIb isoforms, respectively. However, it is not yet clear which training parameters trigger these differential expressions of MHC isoforms. Interestingly, many programmes undertaken by athletes appear to cause a shift towards the MHC I isoform. Increments in the cross-sectional area of muscle after resistance training can be primarily attributed to fibre hypertrophy. However, there may be an upper limit to this hypertrophy. Furthermore, significant fibre hypertrophy appears to follow the sequence of fast twitch fibre hypertrophy preceding slow twitch fibre hypertrophy. Whilst some indirect measures of fibre number in living humans suggest that there is no interindividual variation, postmortem evidence suggests that there is. There are also animal data arising from investigations using resistance training protocols which suggest that chronic exercise can increase fibre number. Furthermore, satellite cell activity has been linked to myotube formation in the human. However, other animal models (i.e. compensatory hypertrophy) do not support the notion of fibre hyperplasia. Even if hyperplasia does occur, its effect on the cross-sectional area of muscle appears to be small. Phosphagen and glycogen metabolism, whilst important during resistance activity appear not to normally limit the performance of resistance activity. Phosphagen and related enzyme adaptations are affected by the type, structure and duration of resistance training. Whilst endogenous glycogen reserves may be increased with prolonged training, typical isotonic training for less than 6 months does not seem to increase glycolytic enzyme activity. Lipid metabolism may be of some significance in bodybuilding type activity. Thus, not surprisingly, oxidative enzyme adaptations appear to be affected by the structure and perhaps the modality of resistance training. The dilution of mitochondrial volume and endogenous lipid densities appears mainly because of fibre hypertrophy.

Topics: Exercise; Glycogen; Humans; Hypertrophy; Lipid Metabolism; Muscles; Myosins; Phosphocreatine; Weight Lifting

Topics: Animals; Cardiomyopathies; Cell Nucleus; Cricetinae; Cytoplasm; DNA; Dogs; Golgi Apparatus; Heart Failure; Humans; Hypertrophy; Hypoxia; Microscopy, Electron; Mitochondria, Muscle; Myocardium; Phosphocreatine; Protein Biosynthesis; Rabbits; Rats; RNA; Sarcolemma

Although recent studies have reported that low-intensity resistance training with blood flow restriction could stress the muscle effectively and provide rapid muscle hypertrophy and strength gain equivalent to those of high-intensity resistance training, the exact mechanism and its generality have not yet been clarified. We investigated the intramuscular metabolism during low-intensity resistance exercise with blood flow restriction and compared it with that of high-intensity and low-intensity resistance exercises without blood flow restriction using (31)P-magnetic resonance spectroscopy. Twenty-six healthy subjects (22 +/- 4 yr) participated and performed unilateral plantar flexion (30 repetitions/min) for 2 min. Protocols were as follows: low-intensity exercise (L) using a load of 20% of one-repetition maximum (1 RM), L with blood flow restriction (LR), and high-intensity exercise using 65% 1 RM (H). Intramuscular phosphocreatine (PCr) and diprotonated phosphate (H(2)PO(4)(-)) levels and intramuscular pH at rest and during exercise were obtained. We found that the PCr depletion, the H(2)PO(4)(-) increase, and the intramuscular pH decrease during LR were significantly greater than those in L (P < 0.001); however, those in LR were significantly lower than those in H (P < 0.001). The recruitment of fast-twitch fiber evaluated by inorganic phosphate splitting occurred in only 31% of the subjects in LR, compared with 70% in H. In conclusion, the metabolic stress in skeletal muscle during low-intensity resistance exercise was significantly increased by applying blood flow restriction, but did not generally reach that during high-intensity resistance exercise. This new method of resistance training needs to be examined for optimization of the protocol to reach equivalence with high-intensity resistance training.

Topics: Adult; Female; Humans; Hydrogen-Ion Concentration; Hypertrophy; Magnetic Resonance Spectroscopy; Male; Muscle Fibers, Fast-Twitch; Muscle Fibers, Skeletal; Muscle, Skeletal; Organ Size; Phosphates; Phosphocreatine; Physical Fitness; Regional Blood Flow; Sex Characteristics; Weight Lifting; Young Adult

Hyperwork of the masseter muscles due to habitual parafunction is thought to induce masseteric hypertrophy (so called work hypertrophy). However, the causes underlying this disease are not yet fully understood. Recently, we had a patient with bilateral masseteric hypertrophy, and we performed a partial excision of the masseter muscles. In this patient's case, we examined muscular activity, energy metabolism, and fiber type composition of the masseter muscles using electromyograms (EMG), 31P-magnetic resonance spectroscopy (MRS), and enzyme-histochemistry. The EMG showed no hyperactivity, and the 31P-MRS showed normal energy spectral patterns and PCr contents of the masseter muscles. The fiber type composition, however, in the muscles in this case was very different from that in muscles with "work hypertrophy" and also that in normal masseter muscles: 1. Loss of type IIB fibers; 2. Increases in type IIA and in type IM & IIC fibers; and 3. Decrease in type I fibers. The findings suggest that this is not a case of work hypertrophy but a case of compensatory hypertrophy possibly due to a lack of high-tetanus-tension type IIB fibers.

Topics: Adenosine Triphosphate; Adult; Electromyography; Energy Metabolism; Histocytochemistry; Humans; Hypertrophy; Magnetic Resonance Spectroscopy; Male; Masseter Muscle; Muscle Contraction; Muscle Fibers, Fast-Twitch; Muscle Fibers, Skeletal; Muscle Fibers, Slow-Twitch; Myosins; Phosphates; Phosphocreatine; Phosphorus Isotopes

During the process of endochondral bone formation, the maturing chondrocyte exhibits profound changes in energy metabolism. To explore the mechanism of energy conservation in cartilage we examined the expression of creatine kinase, an enzyme that catalyzes the formation of ATP in tissues under oxygen stress. Measurement of creatine kinase activity and cytochemical assessment of enzyme distribution clearly showed that the level of enzyme activity was related to chondrocyte maturation. Thus, as the cells hypertrophied, there was a progressive increase in creatine kinase activity. Similarly, an elevation in creatine kinase activity was noted in chondrocyte cultures as the cells assumed an hypertrophic state. When cartilage calcification was disturbed by rickets, there was a decrease in enzyme activity in the hypertrophic region. Studies were performed to examine the creatine kinase isozyme profile of cells of the epiphysis. In resting and proliferating cartilage, the isoform was MM. In hypertrophic cartilage, the predominant isoforms were MB and BB. In terms of the creatine phosphate content, the highest values were seen in the proliferative region; lower amounts were present in hypertrophic and resting cartilage; and no creatine phosphate was detected in calcified cartilage. These data suggest that turnover of creatine phosphate is greatest in the mineralized region of the epiphysis. The results of these investigations point to creatine kinase as being under developmental control. The activity of the enzyme in cartilage cells should serve as a marker of developmental events associated with chondrocyte proliferation, hypertrophy, and mineralization.

Topics: Animals; Cartilage; Cell Division; Cells, Cultured; Chickens; Creatine Kinase; Energy Metabolism; Growth Plate; Histocytochemistry; Hypertrophy; Isoenzymes; Minerals; Phosphocreatine

The urinary bladder depends on intracellular ATP to support a number of essential intracellular processes including contraction. The concentration of ATP is maintained by mitochondrial oxidative phosphorylation, cytosolic glycolysis and the cytosolic activity of creatine kinase, the enzyme that catalysis the rapid transfer of a phosphate from creatine phosphate (CP) to ADP resulting in the formation of ATP. Prior studies in this lab and others have demonstrated that mitochondrial respiration is significantly lower in hypertrophied bladder tissue (induced by partial outlet obstruction of the white New Zealand Rabbit). In addition to decreased mitochondrial respiration, there are significant increases in glycolysis and lactic acid formation in the hypertrophied tissue. In view of the increased glycolysis and decreased mitochondrial function in the hypertrophied tissue, and the importance in creatine kinase in maintaining cytosolic levels of ATP, the current study was designed to determine if outlet obstruction induces any changes in the activity of creatine kinase. The following is a summary of the results: 1) The bladder mass increased from 2.2 +/- 0.2 gm to 11.5 +/- 1.6 gm at 7 days following outlet obstruction. 2) The intracellular concentrations of both ATP and CP were significantly reduced in the bladder tissue following 7 days of obstruction. 3) The percent of protein (per tissue mass) was significantly lower in the obstructed bladders, although the percent of soluble protein was similar. 4) Creatine kinase activity of control bladders showed linear kinetics with a Vmax = 1120 nmoles/mg protein/4 min and Km = 147 microM CP.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Bethanechol Compounds; Creatine Kinase; Cytosol; Electric Stimulation; Hypertrophy; Kinetics; Male; Muscle Contraction; Phosphocreatine; Rabbits; Time Factors; Urethral Obstruction; Urinary Bladder

Attempts have been made to evaluate the role of intracellular creatine in conditions leading to increased or decreased amounts of contractile protein in rat skeletal muscles. Resting concentrations of intracellular creatine ([Cr]i) and creatine phosphate ([CrP]i) were compared in gastrocnemius and soleus muscles with those immediately after a 20-s tetanic stimulation. The hydrolysis of creatine phosphate was the same after heavily and lightly loaded contractions, suggesting that hypertrophy of isometric exercise is not mediated by creatine. With atrophy after denervation or interruption of sciatic axoplasmic flow [Cr]i also remained unchanged, though [CrP]i and the rate of Cr uptake fell after denervation. The major change in adult red and white muscle bulk with unaltered [Cr]i suggests that the Cr sensitivity found by others in developing muscle in vitro has been supplemented or replaced by other control mechanisms.

Topics: Animals; Atrophy; Biological Transport, Active; Creatine; Hypertrophy; Male; Muscle Contraction; Muscle Denervation; Muscles; Organ Size; Phosphocreatine; Rats

Topics: Aging; Aortic Coarctation; Atrophy; Cardiomegaly; Cell Count; Cell Membrane; Cell Physiological Phenomena; Hemodynamics; Hypertrophy; Membrane Potentials; Muscles; Myocardium; Organ Size; Phosphocreatine; Protein Biosynthesis

Topics: Adenosine Triphosphate; Animals; Cardiomyopathies; Cats; Heart Ventricles; Hypertrophy; In Vitro Techniques; Muscles; Papillary Muscles; Phosphocreatine; Pulmonary Artery

Topics: Adenosine Triphosphate; Animals; Cardiomyopathies; Cats; Heart Ventricles; Hypertrophy; In Vitro Techniques; Muscles; Papillary Muscles; Phosphocreatine; Pulmonary Artery

Topics: Cardiomegaly; Coenzymes; Creatine; Creatinine; Hypertrophy; Phosphocreatine