Aging augments interstitial K super(+) concentrations in active muscle of rats

• Published in: Journal of applied physiology (1985) 2006-04, Vol.100 (4), p.1158-1163
• Main Authors: Li, Jianhua, Sinoway, Lawrence I, Ng, Yuk-Chow
• Format: Article
• Language: English
• ISSN: 8750-7587; 1522-1601

Skeletal muscle performance declines with advancing age, and the underlying mechanism is not completely understood. A large body of convincing evidence has demonstrated a crucial role for interstitial K super(+) concentration ([K super(+)] sub(o)) in modulating contractile function of skeletal muscle. The present study tested the hypothesis that during muscle contraction there is a greater accumulation of [K super(+)] sub(o) in aged compared with adult skeletal muscle. Twitch muscle contraction was induced by electrical stimulation of the sciatic nerves of 8- and 32-mo-old Fischer 344 x Brown Norway rats. Levels of [K super(+)] sub(o) were measured continuously by a microdialysis technique with the probes inserted into the gastrocnemius muscle. Stimulation at 1, 3, and 5 Hz elevated muscle [K super(+)] sub(o) by 52, 64, and 88% in adult rats, and by 78, 98, and 104% in aged rats, respectively, and the increase was significantly higher in aged than in adult rats. Recovery for [K super(+)] sub(o), as measured by the time for [K super(+)] sub(o) to recover by 20 and 50% from peak response after stimulation, was slower in aged rats. Ouabain (5 mM), a specific inhibitor of the Na super(+)-K super(+) pump, was added in the perfusate to inhibit the reuptake of K super(+) into the cells to assess the role of the pump in the overall K super(+) balance. Ouabain elevated muscle [K super(+)] sub(o) at rest, and the effect was significantly attenuated in aged animals. The present data demonstrated an augmented [K super(+)] sub(o) in aged skeletal muscle compared with adult skeletal muscle, and the data suggested that an alteration in the function of the Na super(+)-K super(+) pump may contribute, in part, to the deficiency in K super(+) balance in skeletal muscle of aged rats.