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OJVRTM
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.
ABSTRACT
Milner
PI, Fairfax TPA, Wilkins
RJ, Gibson JS,
Effect of oxygen tension
on membrane transport in articular chondrocytes,
Online Journal of Veterinary Research
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