Creatine phosphokinase level in neuromuscular disorders. Effect of dilution and dialysis

Enhancement of skeletal muscle regeneration

We have studied the effect of adding extra satellite cells or soluble factors from crushed muscle on regeneration of minced fragments from rat tibialis muscle. The muscle mince was wrapped in an artificial epimysium to prevent adhesions and cell immigration from adjacent muscles. Regeneration was quantitatively assessed by electrophoretic determination of the muscle-specific form of creatine kinase. Control minces exhibited three periods of change in creatine kinase activity during a 7-week regeneration period. Activity fell rapidly during the first week, then rose gradually from 1-3 weeks and increased more rapidly from 3-7 weeks. To augment the original complement of myogenic cells, satellite cells were isolated from the contralateral muscle, purified by density gradient centrifugation, and expanded in culture for 3 days before adding to the muscle mince. The added cells resulted in a 3-fold enhancement of creatine kinase activity throughout the regeneration period. Soluble muscle extract incorporated into a collagen matrix also stimulated regeneration when added to muscle mince. The extract accelerated the rate of creatine kinase increase during the 1-3 week period beyond that observed in the control or cell augmented mince, suggesting that factors in the extract may facilitate revascularization or reinnervation. The specific activity of creatine kinase was increased in regenerates augmented with both cells and extract, indicating that the effects enhance primarily myogenic processes.

Creatine kinase

Creatine kinase is present in significant concentrations in skeletal muscle and cardiac muscle and to a lesser extent in gastrointestinal tract and brain tissue. The enzyme has been purified from a variety of tissues and an examination of its kinetic and physical properties reveal that the enzyme consists of two subunits and can exist as three isoenzymes containing essential cysteine residues. These properties are important in understanding its stability, the assay conditions, and the techniques used to identify the different isoenzymes. The relationship between the properties and the determination of the enzyme in biological fluids will be a main thrust of the review. Creatine kinase activity in serum rises rapidly in conditions such as acute myocardial infarction and trauma to skeletal muscle. However, the interpretation of such increases is dependent upon a sound knowledge of the factors which influence both the total and isoenzyme activities. The nature of these factors will be discussed in detail.

Radioimmunoassay of creatine kinase: studies on the skeletal muscle and cardiac muscle enzyme (MM and MB isoenzymes) in serum and neuromuscular tissues

A radioimmunoassay, specific for the isoenzymes of creatine kinase containing the M subunit of the enzyme (MM and MB creatine kinase), was employed to determine total creatine kinase concentrations in serum and neuromuscular tissues independently of the state of activity of the enzyme. This technique provides a method for the detection of inactive enzyme, which could be produced by inhibitors of the enzyme or by mutations involving the active site of the enzyme. A series of experiments were carried out to compare the amount of creatine kinase in various samples as assessed by normal enzyme kinetic procedures and by radioimmunoassay. The two techniques yielded equivalent results in all situations tested. Samples included serum from normal subjects and subjects with genetic and acquired diseases of muscle and also extracts from skeletal and cardiac muscle. Small quantities of immunoreactive enzyme were found in nervous tissue and assessed in terms of the incidence of the M subunit.

Plasma lactate in anterior horn cell disease

This communication reports biochemical findings in 7 patients with anterior horn cell disease. The diagnosis was confirmed by evidence of denervation in the EMG and mukle biopsy with normal motor conduction velocities. In 4 of these patients, upper extremities were involved in a symmetrical fashion. In 1, the upper and lower extremities were involved in a symmetrical fashion. In the other 2, one upper or lower extremity were respectively involved in isolation. Pyramidal tract signs were evident in 2 patients of this group. Seventh cranial nerve and 12th cranial nerve involvement were seen in 2 patients. None of the patients manifested 8th cranial nerve dysfunction. All of these 7 patients showed elevation of raised fasting plasma lactate, with normal plasma citrate and plasma pyruvate values. This is in contrast to the altered citrate and pyruvate levels described by other workers in other cases of anterior horn cell disease. The significant biochemical relationship are discussed.

Application of an exponential curve equation for calculation of serum creatine kinase activity

A four-point scale for determination of serum creatine kinase activity is suggested and the application of an exponential curve equation is proposed for cases with this enzyme activity exceeding 177 I.U. The introduction of this modification permits the activity of creatine kinase to be determined in high-activity serum without diluting the serum before determination since this is a source of error in certain muscular diseases.

Serum factors influencing creatine phosphokinase. In vitro studies using diffusates

In vitro studies with diffusates obtained following dialysis of serum samples have enabled us to confirm the presence of inhibiting and activating factors influencing CPK activity. Activating factors are commonly found in many neuromuscular disorders like Duchenne muscular dystrophy (DMD), spinal muscular atrophy and hypothyroid neuromyopathy, and inhibiting factors in dermatomyositis. These findings are further elaborated during serial serum CPK studies after EMG in 3 cases of neurogenic atrophy and 1 case of DMD. The in vivo inhibitory and activating influence of serum factor(s) at 96 and 160 hr respectively after EMG was confirmed by in vitro studies with the diffusates of these serum samples. The functional variations of these diffusates are shown to be related to differences in the composition of these diffusates suggested by paper chromatography.