The response of muscle interstitial prostaglandin E2 (PGE2), prostacyclin I2 (PGI2) and thromboxane A2 (TXA2) levels during incremental dynamic exercise in humans determined by in vivo microdialysis

The microdialysis in vivo technique allows the isolation, purification and quantitative determination of bioactive molecules with low molecular weight ( <20.000 Da) from interstitial fluid (IF) of the muscles. PGE(2) and PGI(2) are vasodilator local hormones, while the TXA(2) is a vasoconstrictor. PGI(2) and TXA(2) are unstable and convert to stable products 6-keto-PGF(1a) and TXB2, respectively. The purpose of this study was to evaluate the response of PGE(2), PGI(2) and TXA(2) in the IF of human muscle (vastus lateralis) during dynamic exercise with a cycle ergometer. In this study two microdialysis probes were inserted with CMA-60 microdialysis catheters into the vastus lateralis muscle of the right leg of eight healthy volunteers aged 24.12.1 years, height 177.5 +/-1.5 cm and body weight 78.1 +/-2.4 kg. After insertion the microdialysis probes perfused at a rate of 3.0 mul/min with Ringer acetate solution. The dialysate fluid was collected a) during the 30' rest period, b) during the 30' exercise period at 100 watts, c) during the 30' exercise period at 150 watts and d) during the 30' rest period after exercise. Our measurements (by the RIA method) showed that the levels of PGE(2) and 6-keto-PGF(1a) in the I.F. of the vastus lateralis muscle increased significantly, while there was a significant decrease in TXB2 during exercise. The changes in the above biomolecules were increased proportionately with the strain of the subject's muscle. Conclusion: Dynamic exercise of the muscles produces a local increase of the vasodilators PGE(2) and PGI(2) while the vasoconstrictor TXA(2) is reduced in the IF of the muscles. This is further evidence that exercise induces propitious biochemical changes. Furthermore, the muscle production of arachidonic acid metabolites during exercise depends on the intensity of the exercise. (C) 2001 Harcourt Publishers Ltd.