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OJVRTM

Online Journal of Veterinary Research©

(Including Medical and Laboratory Research)

Established 1994

ISSN 1328-925X

 

Volume  29 (9): 528-539, 2025.

Control of pH in cartilage chondrocytes of a horse.


Fairfax TPA, Davies ME, Milner P, Gibson JS, Wilkins RJ.

 

University of Oxford, University Laboratory of Physiology, University of Cambridge, Equine Orthopaedic Research Group & Centre for Veterinary Science, Department of Clinical Veterinary Medicine,  Cambridge, UK.

 

ABSTRACT

 

Fairfax TPA, Davies ME, Milner P, Gibson JS, Wilkins RJ. Control of pH in cartilage chondrocytes of a horse. Onl J Vet Res., 29 (9): 528-539, 2025.  We measured intracellular pH (pHi) in chondrocytes in horse cartilage with fluorophore BCECF probe. NH4Cl was used to alter pHi determined in presence or absence of Na+/H+ exchange (NHE) and H+-ATPase inhibitors and HEPES- and HCO3-/CO2 -buffered saline.  We found pHi = 7.18 + 0.02 (n = 6).  On acidification, pH recovered by 26 + 8s (n = 3) but was inhibited by removal of extracellular Na+ or application of HOE694, inhibitor of NHE-1 isoform.  Intrinsic buffering capacity was approximately 20 mmol.(l cells)-1 pH unit-1 at steady-state pHi and was increased at more acidic pHi. Finally, when pH was increased (to about 7.7) with NH4Cl, there was a parallel increase in [Ca2+]i -(of about 60 nM).  The marked sensitivity to HOE694 of recovery from acidosis in both HBS and BBS is consistent with a major role for NHE-1 in pHi homeostasis in equine chondrocytes.  There are also small but significant contributions from H+ -ATPase and HCO3- dependent processes, probably including both HCO3-/Cl- exchange and Na+ -dependent HCO3- transport.  Ca2+ homeostasis is affected by pHi.

 

Key Words: cartilage, horse, chondrocytes – pH – Na+/H+ exchange.

 

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