Mechanism of exercise induced hyperkalemia

[E.S.Prakash]

I was wondering why does exercise cause an increase in plasma [K+]?
Could it be that in active repetitive contraction, Ca2+ remains within
the myocyte hence disrupts the Na-Ca cotransporter and hence the Na-K
pump activity and results in an accumulation of [K+] in the plasma?
This increase in plasma [K+] then activates peripheral chemoreceptors
to stimulate respiration. Is this correct?

Sincerely,

Waye Young

[E.S.Prakash]

Waye Young,

It has been observed that the magnitude of exercise induced
hyperkalemia is a function of exercise intensity, and hyperkalemia in
arterial plasma occurs only with exercise at around peak oxygen
uptake. However, hyperkalemia in venous drainage from exercising
skeletal muscle is noted at lower exercise intensities.

The hyperkalemia is attributed to Na-K ATPase being not able to move
all "K+" brought out during repetitive repolarization. As a
consequence, equilibrium potential of K in contracting muscle moves to
less negative values and this is said to be one contributor to the
onset of muscular fatigue. The rapidity of the decline in plasma [K]
following exercise is also said to reflect Na-K ATPase activity in
recovering muscle.

Reference: Lindinger M, Potassium Regulation During Exercise and
Recovery in Humans: Implications for Skeletal and Cardiac Muscle. In:
Journal of Molecular and Cellular Cardiology, 2007, 1011-1022 [access
via Science Direct]

Yes, there is evidence supporting the possibility that exercise
induced hyperpnea is partly driven by a rise in plasma [K]. See
http://jap.physiology.org/cgi/content/abstract/72/3/811

Best

Prakash
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