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This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 586/6/1715    most recent jphysiol.2007.146753v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Google Scholar Articles by Ingram, K. R. Articles by Levick, J. R. PubMed PubMed Citation Articles by Ingram, K. R. Articles by Levick, J. R. Related Collections Skeletal Muscle and Exercise Related Article

¹ Physiology, Basic Medical Sciences, St George's Hospital Medical School, University of London, London SW17 0RE, UK

The novel hypothesis that the secretion of the joint lubricant hyaluronan (HA) is coupled to movement has implications for normal function and osteoarthritis, and was tested in the knee joints of anaesthetized rabbits. After washing out the endogenous synovial fluid HA (miscibility coefficient 0.4), secretion into the joint cavity was measured over 5 h in static joints and in passively cycled joints. The net static secretion rate (11.2 ± 0.7 µg h^–1, mean ± S.E.M., n = 90) correlated with the variable endogenous HA mass (mean 367 ± 8 µg), with a normalized value of 3.4 ± 0.2 µg h^–1 (100 µg)^–1 . Cyclic joint movement approximately doubled the net HA secretion rate to 22.6 ± 1.2 µg h^–1 (n = 77) and raised the normalized percentage to 5.9 ± 0.3 µg h^–1 (100 µg)^–1. Secretion was inhibited by 2-deoxyglucose and iodoacetate, confirming active secretion. The net accumulation rate underestimated true secretion rate due to some trans-synovial loss. HA turnover time (endogenous mass/secretion rate) was 17–30 h (static) to 8–15 h (moved) The results demonstrate for the first time that the active secretion of HA is coupled to joint usage. Movement–secretion coupling may protect joints against the damaging effects of repetitive joint use, replace HA lost during periods of immobility (overnight), and contribute to the clinical benefit of exercise therapy in moderate osteoarthritis.

(Received 16 October 2007; accepted after revision 13 January 2007; first published online 17 January 2008)
Corresponding author J. R. Levick: Physiology, Basic Medical Sciences, St George's Hospital Medical School, University of London, London SW17 0RE, UK. Email: jlevick{at}sghms.ac.uk

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