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Basolateral anion transport mechanisms underlying fluid secretion by mouse, rat and guinea‐pig pancreatic ducts
Author(s) -
FernándezSalazar M. Paz,
Pascua Patricia,
Calvo José Julián,
López María A.,
Case R. Maynard,
Steward Martin C.,
San Román José I.
Publication year - 2004
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2004.061762
Subject(s) - bumetanide , forskolin , cotransporter , secretin , secretion , medicine , endocrinology , guinea pig , chemistry , dids , ion transporter , extracellular , amiloride , biology , biochemistry , sodium , stimulation , membrane , organic chemistry
Fluid secretion by interlobular pancreatic ducts was determined by using video microscopy to measure the rate of swelling of isolated duct segments that had sealed following overnight culture. The aim was to compare the HCO 3 − requirement for secretin‐evoked secretion in mouse, rat and guinea‐pig pancreas. In mouse and rat ducts, fluid secretion could be evoked by 10 n m secretin and 5 μ m forskolin in the absence of extracellular HCO 3 − . In guinea‐pig ducts, however, fluid secretion was totally dependent on HCO 3 − . Forskolin‐stimulated fluid secretion by mouse and rat ducts in the absence of HCO 3 − was dependent on extracellular Cl − and was completely inhibited by bumetanide (30 μ m ). It was therefore probably mediated by a basolateral Na + –K + –2Cl − cotransporter. In the presence of HCO 3 − , forskolin‐stimulated fluid secretion was reduced ∼40% by bumetanide, ∼50% by inhibitors of basolateral HCO 3 − uptake (3 μ m EIPA and 500 μ m H 2 DIDS), and was totally abolished by simultaneous application of all three inhibitors. We conclude that the driving force for secretin‐evoked fluid secretion by mouse and rat ducts is provided by parallel basolateral mechanisms: Na + –H + exchange and Na + –HCO 3 − cotransport mediating HCO 3 − uptake, and Na + –K + –2Cl − cotransport mediating Cl − uptake. The absence or inactivity of the Cl − uptake pathway in the guinea‐pig pancreatic ducts may help to account for the much higher concentrations of HCO 3 − secreted in this species.