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Effects Of Extracellular Ph On Intervertebrate Discs
Date : 11/12/2015
Author Information
Uploaded by : Mohammed
Uploaded on : 11/12/2015
Subject : Medicine
Extracellular acidity is an important determinant of intervertebral disc matrix turnover, possibly exerting effects through changes of intracellular pHi (pH). There is, however, little information concerning the ways in which these cells regulate their pHi. Fluorimetric techniques have been used in the present study to measure pHi in isolated intervertebral disc cells, and to characterise the membrane transport pathways by which it is regulated. Nucleus pulposus cells were obtained from bovine intervertebral discs by standard enzymatic digestion techniques, and loaded with the pH-sensitive fluoroprobe BCECF. Resting pHi was approximately 6.7 for cells suspended in either HEPES-buffered (HBS) or CO2/HCO3-buffered (BBS) media. Intrinsic buffering capacity was approximately 19 mM pH unitם in HBS and was increased when cells were suspended in BBS. A combination of ion substitution and inhibitor studies for cells at steady-state pHi or acidified by exposure to NH4Cl revealed that in HBS Na+ #215 H+ exchange and an H+-ATPase extrude acid from these cells. Only one of these two systems, the Na+ #215 H+ exchanger, exhibited a sensitivity to pHi, identifying it as the regulator of pHi under these conditions. In BBS, an additional pathway which was dependent on extracellular Na+, extracellular HCO3 and intracellular Clwas detected. These properties are consistent with the four ion HCO3-dependent transporter, although the cation-rich, anion-poor extracellular matrix of the intervertebral disc means that such a pathway has only a marginal role in disc cell pHiregulation.
This resource was uploaded by: Mohammed
Other articles by this author
- The effect of extracellular pH on matrix turnover by cells of the bovine nucleus pulposus
- Regulation of intracellular pH by bovine intervertebral disc cells.