Evidence for sodium-coupled acid-base transport across the basolateral membrane of the reabsorptive duct of the human eccrine sweat gland

Intracellular pH was measured in isolated nonperfused ducts of human eccrin e sweat glands in vitro to investigate basolateral acid-base transport mech anisms. Bath sodium removal led to a bicarbonate-independent, 4-acetamido-4 '-isothiocyanatostilbene-2,2'-disulfonic acid insensitive acidification. Th e recovery of this acidification was ethylisopropyl amiloride sensitive, su ggestive of basolateral sodium:hydrogen exchange. Whereas bath chloride rem oval led to a small acidification this was not 4-acetamido-4-isothiocyanato stilbene-2,2'-disulfonic acid sensitive and its causes remain unclear. Elev ation of bath potassium to depolarize the basolateral membrane led to a sma ll alkalinization but this was not mimicked by addition of barium or chlori de removal. As chloride removal and barium addition would be expected to ca use larger depolarizations than potassium elevation these observations do n ot support a major role for electrogenic acid-base transport. In conclusion , although this study does not support a major role for electrogenic acid-b ase transport, it has demonstrated the basolateral presence of sodium-coupl ed acid-base transport in the reabsorptive duct of the human eccrine sweat gland, which most likely represents a sodium:hydrogen exchanger involved in regulation of intracellular pH.