EVIDENCE FOR A POTASSIUM SHIFT FROM PLASMA TO MUSCLES IN RESPONSE TO AN INCREASED CARBON DIOXIDE TENSION

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Abstract
Frog sartorius muscles, during immersion in frog blood in vitro, usually lose some K. If the control muscles are immersed a short time in blood to permit loss of K from injured fibers and if the blood is equilibrated with a high CO2 tension, then the immersed muscles usually gain K during immersion. If 2 matched sartorius muscles are immersed in frog blood, one at a high and the other at a low CO2 tension, the muscle in the higher CO2 tension shows the higher K content. Measurements of the CO2 combining capacity show that where the K content is high the bicarbonate content is high also by ca. an equivalent amt. Muscles immersed in frog blood containing an increased amt. of K and equilibrated with 5% CO2 show a gain in K representing a diffusion of K into the muscle against a conc. gradient. No evidence for a chloride shift to the muscle could be found. In frog blood isolated sartorius muscles gain considerably in chloride content and their extracellular spaces are increased in vol., although tEis change is less in blood than in Ringer''s soln. It is concluded that an increase in CO2 tension tends to cause K to shift from plasma to muscles, but the same increase in CO2 would cause the K to move from the muscles to Ringer''s soln. because the muscle is intermediate between Ringer''s soln. and blood in its buffering capacity.

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