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Cyclic movement stimulates hyaluronan secretion into the synovial cavity of rabbit joints
Author(s) -
Ingram K. R.,
Wann A. K. T.,
Angel C. K.,
Coleman P. J.,
Levick J. R.
Publication year - 2008
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2007.146753
Subject(s) - secretion , osteoarthritis , synovial fluid , endocrinology , medicine , synovial joint , endogeny , chemistry , pathology , articular cartilage , alternative medicine
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.