Microdialysis and the measurement of muscle interstitial K1 during rest and exercise in humans

Green, Simon, Jens Bülow, and Bengt Saltin. Microdialysis and the measurement of muscle interstitial K1 during rest and exercise in humans. J. Appl. Physiol. 87(1): 460–464, 1999.—The purpose of this study was to examine whether microdialysis and the internal reference thallium-201 (201Tl) could accurately measure muscle interstitial K1 (Ki ) before, during, and after exercise. The relative loss of 201Tl and simultaneous relative recovery of K1 were measured in vitro for 12 microdialysis probes that were bathed in Ringer acetate medium and perfused at various flows (3–10 μl/min). 201Tl loss was linearly related to K1 recovery, and their level of agreement was not different from zero. Microdialysis and 201Tl were then used to measure Ki 1 in the gastrocnemius medialis muscle of four humans during rest and static plantar flexion exercise. At rest, Ki 1 was 3.9–4.3 mmol/l when the perfusate flow was 2 or 5 μl/min. During exercise, Ki 1