Enhanced channelling of sulphate through a rapidly exchangeable sulphate pool in response to stimulated glycosaminoglycan synthesis in pancreatic epithelial cells

The ability of cells to decorate glycosaminoglycans (GAGs) with sulphate in highly specific patterns is important to extracellular matrix biogenesis a nd placing appropriate glycosulphated ligands on the cell surface. We have examined sulphate metabolism in two pancreatic duct epithelial cell lines - PANG-1 and CFPAC-1 (derived from a cystic fibrosis patient) with a view to understanding how pancreatic cells utilise intracellular sulphate. [S-35]S ulphate uptake was rapid and reached near steady state levels within 10 min . However, the intracellular specific activity of [35S]sulphate for PANG-1 and CFPAC-1 reached only 35 and 10%, respectively, of the medium specific a ctivity at 10 min. Therefore, sulphate appears to reside within two compart ments; a rapidly exchangeable sulphate pool (RESP) and a slowly exchangeabl e sulphate pool (SESP). Reducing chloride in the medium, increased the spec ific activity of [S-35]sulphate within cells and increased the size of the inorganic sulphate pool, suggesting that the RESP was enlarged. Sulphate po ols were not different in size between the two cell lines in physiological NaCl. Increasing the size of the sulphate pool had no effect on [S-35]sulph ate: [H-3]glucosamine ratios incorporated into glycosaminoglycans (GAGs); h owever, stimulating the synthesis of GAGs with 4-methylumbelliferyl-beta-D- xyloside, stably elevated [S-35]:[H-3] ratios. This was due to higher [S-35 ]sulphate incorporation. [S-35]Cysteine contributed less than 0.1% of the c ells' sulphate requirements. We conclude that in the face of elevated deman d for sulphate, pancreatic cells appear to channel a greater proportion thr ough the RESP. (C) 1999 Elsevier Science B.V. All rights reserved.