Membrane leakage and increased content of Na -K pumps and Ca in human muscle after a 100-km run

Overgaard, Kristian, Tue Lindstrøm, Thorsten Ingemann-Hansen, and Torben Clausen. Membrane leakage and increased content of Na -K pumps and Ca2 in human muscle after a 100-km run. J Appl Physiol 92: 1891–1898, 2002. First published January 4, 2002; 10.1152/japplphysiol.00669. 2001.—During prolonged exercise, changes in the ionic milieu in and surrounding the muscle fibers may lead to fatigue or damage of the muscle and thereby impair performance. In 10 male subjects, we investigated the effects of 100 km running on muscle and plasma electrolyte contents, muscle Na -K pump content, and plasma concentrations of creatine kinase (CK) and lactate dehydrogenase (LDH). After completion of a 100-km run, significant increases were found in plasma K (from 4.0 0.1 to 5.5 0.2 mM, P 0.001), muscle Na -K pump content (from 334 11 to 378 17 pmol/g, P 0.05), and total muscle Ca2 content (from 0.84 0.03 to 1.02 0.04 mol/g, P 0.001). There was also a large increase in the plasma levels of the muscle-specific enzymes CK and LDH, which reached peak values at the end of the run and lasted several days after the run, indicating that a significant degree of muscle membrane leakage was present. The simultaneous occurrence of raised cellular Ca2 content and muscle membrane leakage supports the theory that Ca2 plays a role in the initiation of degenerative processes in muscles after severe exercise.