Sodium-bicarbonate cotransport in guinea pig ileal crypt cells.
Prior studies show that ileal HCO3- secretion is of crypt origin, possibly involving Na+-HCO3- cotransport. To test for the latter, we isolated crypt cells from guinea pig ileum and determined effects of medium HCO3-, Na+, K+, disulfonic stilbenes, and gramicidin on intracellular pH [pHi;2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein fluorescence], cell volume (electronic sizing), and Na+ efflux from 22Na+ -preloaded cells. Ileal crypt cells alkalinized when placed in sodium gluconate-HCO3- medium containing N-5-methyl-5-isobutyl amiloride (1 microM), bumetanide (10 microM) and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (250 microM which blocks Cl-/HCO3- exchange but not Na+ dependent HCO3- uptake). Depolarization with either gramicidin (50 microM) or 50 mM K+ caused a further 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS)-inhibitable increase in pHi. Gramicidin also caused SITS-inhibitable cell swelling. Both gramicidin effects were Na+ dependent: at 0 mM Na+, gramicidin acidified and did not alter cell volume; at 25 mM, gramicidin also acidified; at 90 and 140 mM, gramicidin alkalinized and induced cell swelling. HCO3- -dependent SITS-inhibitable Na+ efflux from 22Na+ -preloaded cells was also seen. We conclude that ileal crypt cells engage in electrogenic Na+ -HCO3- symport.
MacLeod
R J
RJ
Department of Pediatrics, McGill Univeristy-Montreal Children's Hospital Research Institute, Montreal, Quebec, Canada.
Redican
F
F
Lembessis
P
P
Hamilton
J R
JR
Field
M
M
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D006096:Gramicidin / Q000494:pharmacology; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D007082:Ileum; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D027982:Sodium-Bicarbonate Symporters; D013997:Time Factors
D001639:Bicarbonates; D002352:Carrier Proteins; D027982:Sodium-Bicarbonate Symporters; D002034:Bumetanide; D006096:Gramicidin; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium