Abstract
Uptake of SO by articular chondrocytes is an essential step in the pathway for sulphation of glycosaminoglycans (GAGs), with mutations in SO transport proteins resulting in abnormalities of skeletal growth. In the present study, the transporters mediating SO transport in bovine articular chondrocytes have been characterized. Expression of candidate transporters was determined using RT‐PCR, while SO transport was measured in radioisotope flux experiments. RT‐PCR experiments showed that bovine articular chondrocytes express three transporters known to transport SO: 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 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 efflux of 5 µM was recorded. A DIDS‐sensitive component of SO efflux persisted in solutions lacking Cl^−^ ions. These data are interpreted as evidence for the preferential operation of carrier‐mediated exchange of SO for Cl^−^, while an alternative SO–OH^−^ exchange mode is also possible. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res