The anionic basis of fluid secretion by the rabbit mandibular salivary gland.

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Abstract
The role played by anions in salivary secretion was studied in experiments on the isolated, perfused mandibular gland of the rabbit, in which perfusate Cl- and/or HCO3- were replaced by other anions. Replacement of Cl- with Br- had no significant effect on salivary secretion rate, but replacement with the other anions tested caused secretory rate to fall, by 38% (I-), 50% (NO3-), 61% (isethionate, ise-) and 66% (CH3SO4-), respectively. Replacement of perfusate Cl- with ise- or CH3SO4- caused the salivary HCO3- concentration to rise up to 4-fold. Replacement with Br- or I- seemed to have little effect on salivary HCO3- concentration but, in contrast to ise-, Br- and I- entered the saliva in concentrations comparable to those of Cl- during control perfusion. In glands perfused with HCO3- and ise-, the addition of methazolamide, an inhibitor of carbonic anhydrase, caused a further 60% drop in secretory rate, but the saliva remained rich in HCO3-. Replacement of perfusate HCO3- with Cl- lor ise- had no effect on salivary secretion or composition. Replacement of both HCO3- and Cl- in the perfusate with ise- reduced salivary secretion to less than 2% of control levels. In control glands (i.e., perfused with both HCO3- and Cl-), administration of furosemide, an inhibitor of Na+/Cl- co-transport, reduced the secretion rate and increased salivary HCO3- in a manner indistinguishable from that seen when perfusate Cl- was replaced with ise-. In control perfused glands, administration of SITS (4-acetamino-4''-isothiocyano-2,2''-disulfonic acid stilbene), an inhibitor of Cl-/HCO3- antiports, did not cause any change in salivary HCO3- concentration. Unexpectedly, it induced a significant increase in salivary secretory rate. Salivary secretion evidently depends on 2 independent transport systems. One is a Cl--dependent, furosemide-sensitive system, probably a Na+/Cl- symport. The other is an HCO3--dependent, methazolamide-sensitive system and is probably an Na+/H+ antiport.

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