Abstract
Defective anion transport has recently been put forward as the proximate cause of elevated Cl− in CF sweat. To further explore this possibility, we studied the behaviour of a Cl− analogue, inorganic sulfate (SO4), in serum and sweat obtained from controls (n=22) and adult CF patients (n=6). A minimum of 50 mg of sweat was collected from both forearms onto acid-washed, low-sulfate absorbent disks after the standard pilocarpine electrophoresis. Cl− and SO4 were measured by conductimetric means on the same sample using controlled-flow anion chromatography. Serum Cl− and SO4 were similar in controls and CF patients. In controls, sweat SO4 and Cl− were significantly correlated (r=.52, p<.01). Also, controls had sweat:serum concentration ratios for SO4 (0.28±0.02, x̄±SE) that were not different from Cl− (0.26±0.01), suggesting that both anions are reabsorbed to a similar extent during the formation of the final secretory product from serum ultrafiltrate. As expected, Cl− was raised in CF sweat (104±3 mmol/L vs 19±2 mmol/L in controls, p<.01); however, sweat SO4 was significantly lower in CF patients (48±5 μmol/L) than in controls (81±3 μmol/L, p<.01). Although SO4 and Cl− are known to share the anion exchange system in the red cell membrane and are apparently handled similarly in the normal sweat duct, their transport by the CF sweat duct is not the same. Any model of defective anion exchange in the CF sweat gland must take this dissociation of SO4 and Cl− permeabilities into account.
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Cole, D., Landry, D. DISSOCIATION OF CHLORIDE (Cl-) AND SULFATE (SO4) PER-MEABILITIES IN THE CYSTIC FIBROSIS (CF) SWEAT DUCT. Pediatr Res 18 (Suppl 4), 292 (1984). https://doi.org/10.1203/00006450-198404001-01192
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DOI: https://doi.org/10.1203/00006450-198404001-01192