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Online Journal of Veterinary Research©
Volume 8: 51-58, 2004.
Effect of oxygen tension on membrane transport in articular chondrocytes
aMilner PI, bFairfax TPA, bWilkins RJ, aGibson JS
aCentre for Veterinary Science, Department of Veterinary Medicine, Madingley Road, Cambridge, CB3 0ES, UK and bUniversity Laboratory of Physiology, Parks Road, Oxford, OX1 3PT, UK.
Milner PI, Fairfax TPA, Wilkins RJ, Gibson JS., Effect of oxygen tension on membrane transport in articular chondrocytes, Online J Vet Res 8: 51-58, 2004. Articular chondrocytes experience an O2 tension between 1 and 7% but are usually studied in air (21% O2). We hypothesise that reduction in O2 tension will alter ion homeostasis, via ATP provision or other mechanisms. In this study, therefore, we investigated pHi, H+ and Na+ transport in normoxia and following short term anoxia in primary chondrocytes isolated from slices of articular cartilage. pHi was measured fluorimetrically; Na+ and K+ influx were determined radioisotopically, using 22Na+ and 86Rb+. Resting pHi was unaltered by anoxia (6.93 + 0.15 in oxygenated cells cf 6.89 + 0.07 in N2). When cells were acid loaded by the ammonium prepulse method, pH recovery and Na+/H+ exchanger (NHE) activity were likewise unaltered by O2 tension. Amiloride-sensitive JH was 1.47 + 0.16 mmol.(l cells.min)-1 in air cf 1.12 + 0.25 in N2; NHE activity, measured radioisotopically, was 65.1 + 9.6 nmol.(106 cells.h)-1 in O2 and 65.6 + 9.9 in N2. None of these changes was significant. By contrast, Na+/K+ pump activity was markedly elevated in anoxia: ouabain-sensitive K+ influx was 31.8 + 5.7 nmol.(106 cells.h)-1 in air and 59.6 + 9.9 in N2. These findings represent the first demonstation of O2 sensitive membrane transport in chondrocytes. Their importance is discussed.
KEY WORDS: Oxygen – chondrocyte – ion homeostasis