CPK: here's what I'm talking about

[Tivers@aol.com]

Paper:

Serum and organ creatine phosphokinase alterations in exercise.

Klosak JJ, Penney DG
Rats that swam for 3 h showed a 6-fold increase in serum creatine 
phosphokinase (SCPK) activity which declined to control values within 7 h 
after swimming. Of the excess SCPK, 77% was BB isoenzyme; the remainder was 
mainly MM with traces of MB. Kidney, liver, brain and lung contain mainly BB 
(50-80%) and only a trace of MB (0-7%). Heart CPK was composed of little BB 
(8%) and more MB (28%) and MM (64%). Skeletal muscle CPK was almost entirely 
MM. CPK activity is highest in skeletal muscle, intermediate in heart and 
brain and lowest in kidney, liver and lung. It is suggested that skeletal 
muscle and heart are not involved in CPK release in swimming, and kidney, 
liver and brain may be sites of release. 
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Note the line: "Kidney, liver, brain and lung contain mainly BB (50-80%) "

And the line: "Of the excess SCPK, 77% was BB"

In these rats, nearly 77% of the increase of serum CPK after 3 hours of 
strenuous work was not derived from muscle. Instead, the kidney, brain, liver 
and lungs were implicated. 

When these organs produce CPK underthese circumstances, it is possible that 
they don't also produce the debris that clogs up the kindey and leads to 
kidney failure. Nor will muscle damage occur to the extent of extremely sore 
muscles and slow recovery to previous athletic performance capabilities.  
Theus, a horse experiencing similar distress could conceiveably experience 
very large CPK numbers without experiencing a long term effect on performance 
or kidney health. 

Also note that there was quick recovery to CPK to normal values. With severe 
muscle-derived CPK elevations, the return to normal is much slower.

Also, these rats weren't exercised to the levels of metabolic stress 
endurance horses experience. Thus it is reasonable that very high CPK levels 
could be produced in a similar manner in endurance horses, without concurrent 
muscle damage of significance.

So, if a horse stops, and CPKS are high, then we might focus some attention 
on the fators that would produce lung, brain, liver and kidney damage. there 
may be other isoenzymes that would narrow the field to one of these organs in 
particular. The liver for example, pushed to the max to deliver glucose in 
the face of depleted muscle glycogen and crashing blood glucose. 

ti    


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