Presence of serum creatine kinase isoenzymes in liver failure with cerebral involvement

The enzymology of skeletal muscle disorders

In myopathic disorders, abnormal serum enzyme activities are seen primarily in diseases of skeletal muscle where the condition involves the muscle fibers themselves. In denervation myopathies, serum enzyme activities are usually normal. The most dramatic increases of serum enzymes, particularly creatine kinase, are found in the dystrophic diseases, particularly Duchenne dystrophy. A review is given here of the many causes of abnormal serum enzyme activities where the source of enzymes is believed to be skeletal muscle. These include the dystrophies, various types of trauma, exercise, drug- and poison-induced causes including alcohol, malignant hyperthermia, inflammatory diseases, and miscellaneous causes. Tissue and serum activities are summarized for the commonly performed serum enzymes, i.e., CK, LD, AST, and aldolase. An extensive tabular and current description of the various types of dystrophies is given along with serum CK and pyruvate kinase activities.

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.

Creatine kinase isoenzymes in acute brain injury

Brain-type creatine kinase (CK) isoenzyme (CK-BB) was detected in the serum in 13 out of 26 patients with acute brain injury (50%). The peak of CK-BB activity ranged from 5 to 188 U/liter, constituting, on average, 10.5% of the total CK activity. The highest activities were seen in patients with gunshot wounds. High CK-BB activity was associated with poor prognosis, but minimal CK-BB elevations did not have prognostic significance. Heart-type creatine kinase isoenzyme (CK-MB) was detected in the serum in 17 out of 26 patients (65%). The peak activity ranged from 5 to 115 U/liter, constituting, on average, 6.6% of total CK activity. Electrocardiogram taken from 20 patients revealed transient T-wave inversions in the precordial leads in four patients; three of them also showed serum CK-MB activity. Subendocardial hemorrhage was detected at autopsy in three of the five CK-MB-positive patients, but in none of the four CK-MB-negative cases. Present findings suggest that acute brain injury may be secondarily cause myocardial damage.

Serum creatine kinase isoenzymes behavior in hepatic failure with encephalopathy

Serum creatine kinase isoenzymes were determined in 24 patients with hepatic failure. Hepatic failure was due to severe acute and chronic liver disease. The 24 patients presented different degrees of coma. Nineteen cases (seven hepatitis and 12 cirrhosis) in coma grades III and IV showed the presence in serum of BB, brain and MB, myocardial isoenzymes. Follow up in six of these cases demonstrated that worsening or improvement was accompanied by an increase or decrease of this brain isoenzyme concentration. The leakage from their respective tissues of the brain and myocardial creatine kinase isoenzymes is probably due to the toxic and surface activity properties of serum free fatty acids, bile salts, and bilirrubin, which increase, among other factors, in these pathological entities.

Brain specific creatine kinase isoenzyme behavior in rat serum after bile acid, sodium oleate and albumin injection

In this investigation we have shown that severe liver disease with cerebral involvement can be followed by the presence of BB creatine kinase isoenzyme in serum. Groups of rats were injected with a bile acid mixture, oleic acid, albumin and normal saline respectively. Bile acids or/and oleic acid induced BB isoenzyme to leak from central nervous tissue and this can be measured in serum. Albumin binding prevented this leakage. The experiments support our hypothesis, based on biochemical findings in human liver failure, that detergent and surface activity properties of the above mentioned components are able to produce this specific brain isoenzyme leakage.

Creatine kinase MB isoenzyme in the evaluation of myocardial infarction

The measurement of serum CK-MB isoenzyme is a very sensitive and specific indication of myocardial injury since only myocardium has substantial amounts of CK-MB. Serum CK-MB levels are most helpful clinically when the total creatine kinase is nonspecifically elevated, as with intramuscular injections, cardiac catheterization, stroke, noncardiac surgery and electric cardioversion. Elevations of serum CK-MB occurring in Duchenne's muscular dystrophy and other neuromuscular disorders may be due to the presence of abnormal regenerative skeletal muscle fibers, which are known to contain large amounts of CK-MB isoenzyme. These examples emphasize that under normal, nonregenerative conditions, elevations of serum CK-MB are rare in the absence of myocardial injury.