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Bicarbonate‐dependent pH i regulation by chondrocytes within the superficial zone of bovine articular cartilage
Author(s) -
Simpkin Victoria L.,
Murray Dianne H.,
Hall Andrew P.,
Hall Andrew C.
Publication year - 2007
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.21054
Subject(s) - chemistry , chondrocyte , dids , cartilage , biophysics , bicarbonate , in situ , biochemistry , microbiology and biotechnology , anatomy , membrane , in vitro , biology , organic chemistry
Control of chondrocyte pH (pH i ) determines articular cartilage matrix metabolism. However, the transporters of chondrocytes in situ throughout cartilage zones are unclear, and we tested the hypothesis that chondocytes within the superficial zone (SZ) utilise a HCO 3 − ‐dependent system absent from other zones. Imaging of single BCECF‐labelled cells was used to monitor the pH i of in situ chondrocytes within the cartilage zones, and also that of cells isolated from the SZ or full depth (FD) explants. Resting pH i and intrinsic buffering power (β i ) in HEPES‐buffered saline was not different between SZ and DZ cells, however the pH i of SZ chondrocytes was lower in HCO 3 −saline. Ammonium pre‐pulse was used to acid‐load cells and pH i recovery by in situ or isolated SZ chondrocytes shown to be totally dependent on HCO 3 − . pH i recovery rate was significantly ( P < 0.05) greater for in situ cells, suggesting that isolation damaged the HCO 3 − ‐dependent system. Recovery of pH i by in situ cells was blocked by the anion transport inhibitor DIDS, and partially inhibited by EIPA probably non‐specifically. Recovery of pH i by acidified MZ or DZ cells or those isolated from FD explants was not affected by HCO 3 −( P > 0.05). Na + ‐dependent HCO 3 − ‐(NBC) transporters were identified in SZ chondrocytes by fluorescence immunohistochemistry suggesting that this system might account for the HCO 3 − ‐dependent recovery of pH i . Bovine articular cartilage chondrocytes possess a HCO 3 − ‐dependent transporter which plays a key role in pH i regulation in cells in the SZ, but not in chondrocytes within deeper cartilage zones. J. Cell. Physiol. 212:600–609, 2007. © 2007 Wiley‐Liss, Inc.