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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 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