Creatine phosphokinase measurement

Five repeated exposures of 200 ppm for 12.5 min every 4 d resulted in increased cardiac-specific creatine phosphokinase activity in the blood (pooled data measured at 2 h after the first, third, and fifth exposures) and ectopic heart beats during the first 2 min after injection of norepinephrine (after the fifth exposure) but failed to induce cardiac lesions (histopathologic examinations at 14 d postexposure) (O Flaherty and Thomas 1982). The rats were restrained and anesthetized. 

Example In order to measure the activity of an enzyme E, such as creatine phosphokinase (CPK), the concentration of the substrate S, for instance creatine, should be in large excesses so that the products measured shall be in the linear portion of the curve (Part A ) in Figure 2.5. 

The hrefly Inciferin system is very sensitive and can be conpled to any enzymatic reaction that prodnces or nses ATP. For example, creatine phosphokinase can be determined by this method and hence be nsed in the diagnosis of myocardial infarction and mnscle disorders. The creatine phosphokinase converts AMP into ATP which then nndergoes the reaction with Inciferin as shown in Fignre 3.25. ATP pro-dnction is essential for every known life form and the firefly Inciferin system can be nsed to check for microbial life. Hence systems have been developed that use a portable luminescence workstation to monitor sanitation in food manufacturing and to check for sterile environments in technological workplaces. The system can also be applied in checking cell viability, for instance in cell cultures and to measure the toxic effects of chemicals on cells. 

Biocompatibility of injectable formulations with tissues can be tested by observing microscopic histology of the tissues so exposed, or by using erythrocyte hemolysis as a surrogate for these other tissues. Alternatively, one can measure the level of the cytosolic enzyme creatine phosphokinase that is released from damaged tissues (18). 

There may be an association between metamfetamine abuse and rhabdomyolysis. In a retrospective review of 367 patients with rhabdomyolysis, 166 were positive for metamfetamine (78). They had higher mean initial and lower mean peak activities of creatine phosphokinase. There was no significant difference in the incidence of acute renal insufficiency. The authors suggested screening all patients with rhabdomyolysis of unclear cause for metamfetamine and measuring creatine phosphokinase activity. 

Adenosine triphosphate creatine A-phosphotransferase (EC 2.7.3.2), also creatine phosphokinase. Creatine kinase is found in muscle and is responsible for the formation of creatine phosphate from creatine and adenosine triphosphate creatine phosphate is a higher energy source for muscle contraction. Creatine kinase is elevated in all forms of muscular dystrophy. Creatine kinase is dimer and is present as isozymes (CK-1, BB CK-2, MB CK-3, MM) and Ck-mt (mitochondrial). Creatine kinase is also used to measure cardiac muscle damage in myocardial infarction. See Bais, R. and Edwards, J.B., Creatine kinase, CRC Crit. Rev. Clin. Lab. ScL 16, 291-355, 1982 McLeish, M.J. and Kenyon, G.L., Relating structure to mechanism in creatine kinase, Crit. Rev. Biochem. Mol. Biol 40, 1-20, 2005. 

Enzymes, which are normally produced in cells, are released into the blood when cells are injured. For example, after a heart attack, there is an increase in blood levels of creatine phosphokinase (CPK) and other enzymes such as lactate dehydrogenase (LDH). The extent of damage and the rate of recovery can be estimated by periodically measuring the levels of these enzymes. Measurement of the MB isozyme of CPK is also used as an aid in diagnosis. 

Creatine phosphokinase (CK), one of the proteins measured to follow Ann Jeina s myocardial infarction (see Chapter 6) is present in cells as dimers (two subunits). The dimers may be homodimers (two identical subunits of either the M [muscle] isozyme or the B [brain] isozyme), or heterodimers (MB) The MB isozyme is produced only by the heart and readily released from injured cardiomyocytes into the blood (see Chapter 6). 

The authors also measured the activity of serum glutamic oxalacetic transaminase (SCOT), creatine phosphokinase (CPK), and lactic dehydrogenase (LDH) to determine if there was evidence of myocardial necrosis. They... 

According to inpatient records from St. Luke s Hospital, the most common laboratory finding related to sarin toxicity was a decrease in plasma cholinesterase (ChE) levels in 74% of patients. In patients with more severe toxicity, plasma ChE levels tended to be lower, but a more accurate indication of ChE inhibition is the measurement of erythrocyte ChE, as erythrocyte acetylcholinesterase (AChE) is considered "true ChE" and plasma ChE is "pseudo-ChE." However, erythrocyte ChE is not routinely measured, whereas plasma ChE is included in many clinical chemistry panels thus, it can be used as a simple index for ChE activity. In both the Matsumoto and Tokyo subway sarin attacks, plasma ChE served as a useful index of sarin exposure. In 92% of hospitalized patients, plasma ChE levels returned to normal on the following day. In addition, inpatient records from St. Luke s Hospital showed an elevated creatine phosphokinase and leukocytosis in 11% and 60% of patients, respectively. In severe cases such as the Matsumoto attack, hyperglycemia, ketonuria, and low serum triglycerides due to tire toxic effects of sarin on the adrenal medulla were observed (Yanagisawa et al, 2006). 

---