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Characterization of sulphate transporters in isolated bovine articular chondrocytes
Author(s) -
Meredith David,
Gehl Katharina A.,
Seymour John,
Ellory J. Clive,
Wilkins Robert J.
Publication year - 2007
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.29388
Subject(s) - dids , chemistry , efflux , transporter , chondrocyte , ion transporter , extracellular , biochemistry , glycosaminoglycan , sulfation , biophysics , microbiology and biotechnology , biology , membrane , in vitro , gene
Uptake of SO 4 2−by articular chondrocytes is an essential step in the pathway for sulphation of glycosaminoglycans (GAGs), with mutations in SO 4 2−transport proteins resulting in abnormalities of skeletal growth. In the present study, the transporters mediating SO 4 2−transport in bovine articular chondrocytes have been characterized. Expression of candidate transporters was determined using RT‐PCR, while SO 4 2−transport was measured in radioisotope flux experiments. RT‐PCR experiments showed that bovine articular chondrocytes express three transporters known to transport SO 4 2− : AE2 (SLC4a2), DTDST (SLC26a2), and SLC26a11. Other transporters—NaS‐1 (SLC13a1), SAT‐1 (SLC26a1), DRA (SLC26a3), SLC26a6 (PAT1), SLC26a7, SLC26a8 (Tat‐1), and SLC26a9—were, however, not detected. In functional experiments, SO 4 2−uptake was temperature‐sensitive, inhibited by 60% by DIDS (50 µM) and exhibited saturation kinetics, with a K m value of 16 mM. Uptake was also inhibited at alkaline extracellular pH. In further experiments, a K i value for DIDS inhibition of SO 4 2−efflux of 5 µM was recorded. A DIDS‐sensitive component of SO 4 2−efflux persisted in solutions lacking Cl − ions. These data are interpreted as evidence for the preferential operation of carrier‐mediated exchange of SO 4 2−for Cl − , while an alternative SO 4 2− –OH − exchange mode is also possible. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res