Alterations in the mRNA levels of two metabolic enzymes in rat skeletal muscle during stretch-induced hypertrophy and disuse atrophy

A quantitative study of bioenergetics in skeletal muscle lacking carbonic anhydrase III using 31P magnetic resonance spectroscopy

Oxidative slow skeletal muscle contains carbonic anhydrase III in high concentration, but its primary function remains unknown. To determine whether its lack handicaps energy metabolism and/or acid elimination, we measured the intracellular pH and energy phosphates by (31)P magnetic resonance spectroscopy in hind limb muscles of wild-type and CA III knockout mice during and after ischemia and intense exercise (electrical stimulation). Thirty minutes of ischemia caused phosphocreatine (PCr) to fall and P(i) to rise while pH and ATP remained constant in both strains of mice. PCr and P(i) kinetics during ischemia and recovery were not significantly different between the two genotypes. From this we conclude that under neutral pH conditions resting muscle anaerobic metabolism, the rate of the creatine kinase reaction, intracellular buffering of protons, and phosphorylation of creatine by mitochondrial oxygen metabolism are not influenced by the lack of CA III. Two minutes of intense stimulation of the mouse gastrocnemius caused PCr, ATP, and pH to fall and ADP and P(i) to rise, and these changes, with the exception of ATP, were all significantly larger in the CA III knockouts. The rate of return of pH and ADP to control values was the same in wild-type and mutant mice, but in the mutants PCr and P(i) recovery were delayed in the first minute after stimulation. Because the tension decrease during fatigue is known to be the same in the two genotypes, we conclude that a lack of CA III impairs mitochondrial ATP synthesis.

Effect of Heat in Increasing the Range of Knee Motion After the Development of a Joint Contracture: An Experiment With an Animal Model

OBJECTIVE

To compare the effects of 2 different heat modalities, infrared and ultrasonic therapy, on a knee flexion contracture.

DESIGN

In vivo, experimental, controlled study involving a rat knee joint contracture model that was immobilized using a ligature in flexion for 40 days.

SETTING

Collegiate research laboratory.

ANIMALS

Ninety-three adult male Wistar rats.

INTERVENTIONS

After remobilization, rats were assigned to 3 treatment groups: stretching only (S), stretching with infrared therapy (S+IR), and stretching with ultrasonic therapy (S+US). Six treatment sessions were given in 2 weeks.

MAIN OUTCOME MEASURES

The angle of maximum knee extension, wet-weight of triceps surae muscles, phase lag, and dynamic stiffness as mechanical responses were measured, and histologic study was conducted.

RESULTS

Compared with the S group, both the S+IR and S+US groups exhibited a significant increase in range of motion (ROM) (P=.021, P=.008, respectively) and a tendency to decrease the phase lag, but there was no significant difference between the 2 heat-combined groups. There were no differences in the weights of the triceps surae muscles and in dynamic stiffness among the groups.

CONCLUSIONS

Six treatment sessions of stretching with infrared or ultrasound were more effective than stretching without heat at increasing the ROM and decreasing the phase lag of a moderately severe joint contracture. The clinical implementation of heat is advocated to regain a normal ROM and mechanical property when experiencing a joint contracture.

Quantitative changes in the mRNA for contractile proteins and metabolic enzymes in masseter muscle of bite-opened rats

To study the effects of bite opening on the fibre phenotypes of rat masseter, the mRNAs of four predominant myosin heavy-chain isoforms (MHC I, IIa, IId/x and IIb) and two alkali light-chain isoforms (LC1f and 3f) as well as those of two metabolic enzymes, carbonic anhydrase III (CAIII, oxidative enzyme) and glucose-phosphate isomerase (GPI, glycolytic enzyme), were measured in relation to the total RNA of masseter muscle by competitive, reverse transcriptase-polymerase chain reaction in control and bite-opened rats. Bite opening (2.8 mm increase in the vertical dimension for 1 week) significantly (P<0.05) increased the amount of MHC IIa mRNA but decreased (P<0.001) the amount of MHC IIb mRNA without changing the amount of MHC IId/x mRNA. No MHC I mRNA was found in any masseter studied. A significant (P<0.01) increase in the mRNA of LC1f associated with a decrease (P<0.05) in that of LC3f was observed after the bite opening. The CAIII mRNA increased significantly (P<0.001), while the GPI mRNA decreased (P<0.05) in association with the bite opening. These results strongly suggest that in 1 week of bite opening changes the rat masseter muscle from a glycolytic, MHC IIb-LC3f-dominant fibre to an oxidative, MHC IIa-LC1f-dominant fibre.

Proteomic analysis of the atrophying rat soleus muscle following denervation

A proteomic analysis was performed comparing normal rat soleus muscle to denervated soleus muscle at 0.5, 1, 2, 4, 6, 8 and 10 days post denervation. Muscle mass measurements demonstrated that the times of major mass changes occurred between 2 and 4 days post denervation. Proteomic analysis of the denervated soleus muscle during the atrophy process demonstrated statistically significant (at the p < 0.01 level) changes in 73 soleus proteins, including coordinated changes in select groups of proteins. Sequence analysis of ten differentially regulated proteins identified metabolic proteins, chaperone and contractile apparatus proteins. Together these data indicate that coordinated temporally regulated changes in the proteome occur during denervation-induced soleus muscle atrophy, including changes in muscle metabolism and contractile apparatus proteins.