kreatinkininas

Creatine kinases, or kreatinkininas, are a family of enzymes that catalyze the transfer of a phosphate group from phosphocreatine to adenosine diphosphate, regenerating ATP. They play an important role in cellular energy buffering, especially in tissues with high and fluctuating energy demands such as skeletal muscle, heart, and brain. Serum creatine kinase (CK) activity is commonly measured as a marker of tissue injury, but the source of the damage is often inferred from CK isoenzymes.

The three major CK isoenzymes are CK-MM (muscle type), CK-MB (cardiac muscle), and CK-BB (brain). In clinical testing, a rise in total CK with a higher CK-MB fraction can point to cardiac injury, while a predominance of CK-MM suggests skeletal muscle damage. CK-BB testing is less commonly used today, because its interpretation in serum is less specific for brain injury.

Measurement and interpretation: CK activity is determined by immunoassay or electrophoretic methods, and normal reference ranges vary by laboratory, age, sex, muscle mass, and recent physical activity. CK levels can be elevated in a variety of conditions beyond myocardial infarction, including muscular dystrophy, inflammatory myopathies, rhabdomyolysis, seizures, major trauma, and after intense exercise or intramuscular injections.

Clinical use and limitations: CK is a historical and supportive marker for tissue damage. In myocardial infarction, CK-MB was used in the past, but troponins are now preferred for diagnosis due to greater specificity. CK measurements remain useful for monitoring muscle disease progression and the response to therapy, with isoenzyme analysis providing additional, though not definitive, localization of tissue injury.