Arterial pressure responses to increasing interstitial potassium in hindlimb muscle of dogs

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Abstract
Static contraction of hindlimb skeletal muscle is known to increase reflexly arterial pressure and heart rate. K is known to be released by the working muscle and is thought to activate the afferents responsible for the reflex cardiovascular responses to muscular contraction. However, it is not known whether K, at interstitial concentrations within the range observed during static contraction, is capable of stimulating these afferents. Thus, K was injected into the gracilis artery of chloralose-anesthetized dogs while interstitial K concentrations were measured in the gracilis muscle with K-selective electrodes. In 16 dogs, it was found that K injections, which increased interstitial K concentrations by 4.7 .+-. 0.3 mM, increased mean arterial pressure by 18 .+-. 3 mmHg and heart rate by 12 .+-. 8 beats/min; cutting the obturator nerve abolished these increases. These heart rate and blood pressure responses were of short duration (20 .+-. 7 s), even though interstitial K remained elevated for a period of several minutes. In 5 of the 16 dogs, static contraction of the gracilis muscle for 60 s increased interstitial K concentration by 4.3 .+-. 0.3 mM. Potassium may play a role in causing the reflex cardiovascular responses to static muscular contraction.

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