Bicarbonate transport by the human pancreatic ductal cell line HPAF.
OBJECTIVE
The human pancreatic duct cell line, HPAF, has been shown previously to secrete Cl(-) in response to Ca(2+)-mobilizing stimuli. Our aim was to assess the capacity of HPAF cells to transport and secrete HCO3(-).


METHODS
HPAF cells were grown as confluent monolayers on permeable supports. Short-circuit current was measured by voltage clamp. Intracellular pH (pHi) was measured by microfluorometry in cells loaded with 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF).


RESULTS
In HCO3(-)-free solutions, ATP-evoked changes in short-circuit current were inhibited by bumetanide, and the recovery of pHi from acid loading was abolished by 5-(N-ethyl-N-isopropyl)-amiloride (EIPA). In the presence of HCO3(-), ATP-evoked secretion was no longer inhibited by bumetanide, and there was a strong EIPA-insensitive recovery from acid loading, which was inhibited by 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulfonate (H2DIDS). ATP, but not forskolin, stimulated HCO3(-) efflux from the cells.


CONCLUSIONS
In the absence of HCO3(-), ATP-evoked Cl(-) secretion is driven by a basolateral Na(+)-K(+)-2Cl(-) cotransporter, and pH(i) is regulated by apical and basolateral Na(+)/H(+) exchangers. In the presence of HCO3(-), ATP-evoked secretion is sustained in the absence of Na(+)-K(+)-2Cl(-) cotransporter activity and is probably driven by basolateral Na(+)-HCO3(-) cotransport.
Demeter
Irma
I
Department of Oral Biology, Semmelweis University, Budapest, Hungary.
Hegyesi
Orsolya
O
Nagy
Akos Károly
AK
Case
Maynard R
MR
Steward
Martin C
MC
Varga
Gábor
G
Burghardt
Beáta
B
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D001639:Bicarbonates / Q000378:metabolism* / Q000493:pharmacokinetics*; D001692:Biological Transport / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D045744:Cell Line, Tumor; D002712:Chlorides / Q000378:metabolism; D003592:Cytophotometry; D005452:Fluoresceins / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D042541:Intracellular Space / Q000737:chemistry; D017136:Ion Transport / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D010183:Pancreatic Ducts / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000494:pharmacology; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism; D064506:Solute Carrier Family 12, Member 2
D001639:Bicarbonates; D002712:Chlorides; D005452:Fluoresceins; C578877:SLC12A2 protein, human; D049994:Sodium Potassium Chloride Symporter Inhibitors; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D002034:Bumetanide; C018564:dihydro-DIDS; D000584:Amiloride; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D000255:Adenosine Triphosphate; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; C039614:ethylisopropylamiloride