Microdialysis of skeletal muscle at rest

Techniques in human skeletal muscle research are by necessity predominantly 'descriptive Microdialysis has raised high expectations that it could meet the demand for a method that allows 'mechanistic' investigations to be per formed in human skeletal muscle. In the present review, some views are give n on how well the initial expectations on the use of the microdialysis tech nique in skeletal muscle have been fulfilled, and the areas in which additi onal work is needed in order to validate microdialysis as an important meta bolic technique in this tissue. The microdialysis catheter has been equated to an artificial blood vessel, which is introduced into the tissue. By mea ns of this 'vessel' the concentrations of compounds in the interstitial spa ce can be monitored. The concentration of substances in the collected sampl es is dependent on the rate of perfusate flow. When perfusate flow is slow enough to allow complete equilibration between interstitial and perfusate f luids, the concentration in the perfusate is maximal and identical to the i nterstitial concentration. Microdialysis data may be influenced by changes in blood flow, especially in instances where the tissue diffusivity limits the recovery in vivo, i.e, when recovery in vitro is 100 %, whereas the rec overy in vivo is less than 100 %. Microdialysis data indicate that a signif icant arterial-interstitial glucose concentration gradient exists in skelet al muscle but not in adipose tissue at rest. While the concentrations of gl ucose and lactate in the dialysate from skeletal muscle are close to the ex pected values, the glycerol values obtained for muscle are still puzzling. Ethanol added to the perfusate will be cleared by the tissue at a rate that is determined by the nutritive blood flow (the microdialysis ethanol techn ique). It is concluded that microdialysis of skeletal muscle has become an important technique for mechanistic studies in human metabolism and nutriti on.