الفهرس 
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Abstract
Skeletal (or striated) muscles are attached to bones being responsible for the axial and appendicular movement of the skeleton and for maintenance of body position and posture. In addition, skeletal muscles of the eye (extra-ocular muscles) provide precise eye movement.
Skeletal muscle consists of parallel muscle fibers, arranged in bundles or fascicles and separated by C.T. septa, the perimysium. The fibers are connected together by C.T., endomysium, while the whole muscle is covered by a C.T. covering, the epimysium. The C.T. carries blood vessels and nerves to the muscle and it aids in integrating and transmitting the force of muscular contraction through binding the muscle units together.
Longitudinal sections of skeletal muscles show that the muscle fiber is an elongated cylindrical multinucleated cell which has up to 100 nuclei peripherally located. Cytoplasm (Sarcoplasm) is acidophilic with clear transverse striations.
By E/M skeletal muscle fibers contain primarily long cylindrical filament bundles, called myofibrils, running to the long axis of the fiber. Sarcoplasmic reticulum and mitochondria are arranged in rows between the myofibrils and with negligible amount of RER and Ribosomes. There is abundant myoglobin and a large amount of glycogen that serves as reserve of energy during muscle contraction.
Longitudinally sectioned skeletal muscle fibers show alternating dark (A bands) and light (I bands) bands. This banding pattern is due mainly to
the regular arrangement of thick and thin myofilaments, composed of myosin and F-actin, respectively that lie parallel to the long axis of the myofibrils in a symmetric pattern.
In skeletal muscle, the smooth endoplasmic reticulum (sarcoplasmic reticulum) is specialized for Ca2+ ion sequestration. The depolarization of this sarcoplasmic reticulum membrane, which results in the release of Ca2+ ions, is initiated at the specialized motor nerve synapses on the sarcolemma. Surface-initiated depolarization signals would have to diffuse throughout the cell to produce Ca2+ release from internal sarcoplasmic reticulum cisternae. To provide for a uniform contraction, skeletal muscle fibers have a system of transverse (T) tubules. These long fingerlike invaginations of the sarcolemma penetrate deeply into the sarcoplasm and encircle every myofibril near the A-I band boundaries of each sarcomere. Adjacent to each side of every T tubule are expanded terminal cisterns of the sarcoplasmic reticulum. In longitudinal TEM sections, this complex of a T tubule with two closely associated small cisterns of sarcoplasmic reticulum on each side is known as a triad.
Skeletal muscle fibers vary in colour (red, white and intermediate) depending on their content of myoglobin. Skeletal muscle fibers contract with different velocities, depending on their ability to split Adenosine Triphosphate (ATP). Faster contracting fibers have greater ability to split ATP. In addition, skeletal muscle fibers vary with respect to the metabolic processes they use to generate ATP. They also differ in terms of the onset of fatigue. Based on various structural and functional characteristics, skeletal muscle fibers are classified into three types: Type I fibers, Type II A fibers and type II B fibers.
Statins are the drugs of choice for the management of hypercholesterolaemia because of their proven efficacy and safety profile. They also have an increasing role in managing cardiovascular risk in patients with relatively normal levels of plasma cholesterol. Statins target hepatocytes and inhibit 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, the enzyme that catalyses the conversion of HMG-CoA to mevalonate, the rate-limiting step in de novo cholesterol synthesis. The reduction of cholesterol in hepatocytes leads to the increase of hepatic LDL receptors that determines the reduction of circulating LDL and its precursors.
Statins can produce an unexplained myopathy with symptoms ranging from mild myalgia to fatal rhabdomyolysis. The mechanism by which statins cause muscle toxicity is not well understood. Individual statins may have distinct effects on the synthesis of coenzyme Q10, which plays an important role in muscle cell energy production.
Rosuvastatin is a fully synthetic HMG-CoA reductase inhibitor. It belongs to a new generation of methane-sulphonamide Pyrimidine and N-methane sulfonyl pyrrole-substituted 3, 5- dihydroxy-heptenoates. Although the characteristic statin pharmacophore remains similar to other statins, the addition of a stable polar methane-sulphonamide group provides low lipophilicity and enhanced ionic interaction with HMG-CoA reductase enzyme thus improving its binding affinity to this enzyme. Rosuvastatin is less likely to cause metabolic drug to drug interactions since it has limited metabolism by Cytochrome P450 isoenzymes.
Coenzyme Q10 is a lipid compound with 10 isoprenoid units which is widely distributed in the human body. It is a lipophilic inner mitochondrial membrane cofactor that is used to shuttle electrons in the formation of ATP. It has also been shown to have important antioxidant properties. Physiologic
concentrations of coenzyme Q10 do not fully saturate the mitochondrial receptors. Accordingly, even a small increase in the coenzyme Q10 concentration of mitochondrial membranes can lead to an increase in mitochondrial respiration. This observation may be the biochemical mechanism by which exogenous coenzyme Q10 administration has in some studies improved mitochondrial myopathies and cardiomyopathies.
Materials and Methods:
This study included included 54 male albino rats weighting 100-150g. The rats were divided into four main groups:
- group I (control group):
It was comprised of 18 rats; divided into 3 subgroups:
Subgroup Ia: 6 rats received no treatment for 12 weeks.
Subgroup Ib: 6 rats received 2ml water containing 0.5% hydroxypropyl methylcellulose by oral route for 12 weeks.
Subgroup Ic: 6 rats received 2 ml soybean oil by oral route for 12 weeks.
- group II (coenzyme Q10 treated):
It was comprised of 12 rats. Each rat received coenzyme Q10 at a dose of 3 mg/day by oral route for 12 weeks and served as + ve control group.
- group III (Rosuvastatin treated):
It was comprised of 12 rats. Each rat received rosuvastatin at a dose of 0.5 mg/day by oral route.
Rats were divided into 2 equal subgroups:
group IIIa: 6 rats were sacrificed after 4 weeks.
group IIIb: 6 rats were sacrificed after 12 weeks.
- group IV (Rosuvastatin and coenzyme Q10 treated) :
It was comprised of 12 rats. Each rat received rosuvastatin and coenzyme Q10 at the same previous doses and the same route of administration.
Rats were divided into 2 equal subgroups:
group IVa: 6 rats were sacrificed after 4 weeks.
group IVb: 6 rats were sacrificed after 12 weeks.
At the end of each detected period, rats were sacrificed by cervical dislocation then gastrocnemius muscles were obtained, rapidly fixed in 3% glutaraldehyde for 3 hours, and then processed for Electron Microscopic Study. Other tissue samples were fixed in 10% formol saline, washed in tap water, dehydrated in ascending grades of alcohol, cleared in xylene, impregnated in soft paraffin for 45 minutes followed by hard paraffin for 45 minutes, then embedded in hard paraffin and oriented in blocks. Paraffin sections of 5-6 micrometer thickness were cut for light microscope studies.
Results:
Light microscopic results:
group I & II:
Examination of H&E stained sections of the gastrocnemius muscle of the two groups revealed the normal structure of the skeletal muscle. It was formed of bundles of muscle fibers separated by connective tissue (C.T.), perimysum. The fibers were connected together by (C.T.), endomysium. Some blood vessels were
seen in the connective tissue partitions of the muscle. In cross sections skeletal muscle fibers appeared polygonal with peripheral nuclei. In longitudinal sections the skeletal muscle fibers appeared parallel, long, cylindrical and multinucleated with minimal variation in fiber size. The sarcoplasm of the muscle fibers appeared acidophilic and crossly striated. The nuclei were elongated and peripheral in position under the sarcolemma.
In Mallory’s trichrome stained sections minimal amount of collagen fibers were present in-between muscle fibers.
group IIIa &b (Ros. treated groups for 4 &12 weeks respectively):
Examination of sections of gastrocnemius muscle of subgroup IIIa showed focal areas of degeneration with nearly normal arrangement of other skeletal muscle fibers. There were some haemorrhagic spots, associated with mononuclear cellular infiltration. Splitting of the muscle fibers and loss of transverse striations appeared in a longitudinal section associated with small pyknotic nuclei. A transverse section of the muscle fibers showed variation in size and shape of the fibers with extensive deposition of collagen fibers within the perimysium. Blood vessels appeared dilated and congested. Another transverse section showed distorted architecture and indistinct borders of the muscle fibers.
By Mallory’s trichrome stain, transverse sections of the muscle showed mild to moderate amount of collagen fibers inbetween muscle fibers and in the perimysium.
After 12 weeks of treatment (Subgroup IIIb), the changes involved wider areas. Muscle fibers were more widely separated from each other with loss of striations. There were areas of complete degeneration and heavy mononuclear cellular infiltration. Clear vacuolation was observed. Homogenization and splitting of some fibers associated with internal nuclei were also obvious, while nuclear degeneration with loss of normal architecture of muscle was detected.
Mallory’s trichrome stain revealed marked increase in collagen fibers inbetween muscle fibers and bundles.
group IVa&b (Ros. & CoQ10 treated groups for 4 &12 weeks respectively):
The histological picture of gastrocnemius muscle of subgroup IVa was more or less similar to control except minimal disintegration of muscle fibers. Internal nuclei forming a nuclear chain were noticed. Muscle fibers with peripheral condensed nuclei associated with blood vessel congestion were detected. Deposition of collagen fibers was mild.
After 12 weeks of drugs administration (subgroup IVb), the H&E sections showed mild focal histological changes. A transverse section showed partial distortion and splitting of some fibers. Areas of loss of transverse striations were observed in a longitudinal section associated with mononuclear cellular infiltration and some hemorrhagic spots. Mild to moderate deposition of collagen fibers was seen by Mallory’s trichrome stain.
Electron microscopic results:
group I & II:
Electron microscopic examination of gastrocnemius muscle of these groups showed normal ultrastructure. The sarcoplasm appeared filled with myofibrils arranged parallel to the long axis of the myofiber. The myofibrils showed regular arrangement of alternating light and dark bands. A pale narrow region, the H band, was seen transecting the A band with a dark M-line within it. Z-line was seen bisecting the light band. Sarcomeres were seen between two successive Z-lines. Oval nuclei were seen under the sarcolemma, with their heterochromatin distributed along the inner surface of the nuclear envelope and one or two nucleoli could be noticed. Mitochondria were arranged in pairs around Z-line and few
mitochondria were also observed at the subsarcolemmal area. Vesicles of sarcoplasmic reticulum were found between the myofibrils.
group IIIa &b (Ros. treated groups for 4 &12 weeks respectively):
Electron microscopic examination of gastrocnemius muscle of Subgroup IIIa showed focal disorganization and discontinuation of myofibrils together with focal areas of disruption of Z-lines, T-tubules were seen. The sarcoplasm was loaded with mitochondria of variable size and shape in the subsarcolemmal space and inbetween myofibrils.There were dilated cisternae of the sarcoplasmic reticulum and blood vessel congestion. Glycogen granules deposition was also detected.
Electron microscopic examination of gastrocnemius muscle of subgroup IIIb showed partial loss of myofibrils with disappearance of their Z-lines and two t-tubules were seen per each sarcomere. There was dilatation of sarcoplasmic reticulum cisternae. Internal nucleus with irregular nuclear envelope and condensed heterochromatin was found in some fibers. Fusion of the mitochondria to form giant vacuolated ones was very obvious. Diffuse glycogen granules were observed especially in the subsarcolemmal space and also in the intermyofibrillar spaces.
group IVa&b (Ros. & CoQ10 treated groups for 4 &12 weeks respectively):
After 4 weeks of treatment (subgroup IVa), small number of fused mitochondria between myofibrils were seen. Otherwize, the arrangement of myofibrils was similar to control.
After 12 weeks of drugs administration (subgroup IVb), electron microscopic examination revealed apparent dilatation of some sarcoplasmic reticulum cisternae, few vacuolated mitochondria and mild loss of myofibrils.