Evidence for apical Na+/H+ exchanger in bovine main pancreatic duct.
The finding of a high PCO2 in basally secreted pancreatic juice of man and dog raises the hypothesis of proton secretion from ductal epithelial cells presumably through a Na+/H+ exchanger. To test this possibility, H+ luminal secretion and Na+ movements were measured in vitro on samples of bovine pancreatic ducts mounted in Ussing-type chambers. The rate of luminal acidification measured by the pH stat method, using bicarbonate-free media gassed with 100% O2, reached 2.75 muEq/cm2/hr. Proton secretion was blocked in the presence of 1 nM amiloride or in the absence of Na+ (replaced by choline) in the mucosal solution. Study of transepithelial 22Na fluxes in short-circuited tissue, bathed on both sides by control Ringer solution, gassed by 95% O2-5% CO2 demonstrated a net sodium transport from the mucosal to the interstitial side of the duct (net 22Na flux = 3.23 +/- 0.8 muEq/cm2/hr). This net sodium transport was electroneutral and blocked by mucosal amiloride (0.5-1 mM/liter) or by interstitial ouabain (1 mM/liter). These results are consistent with the existence of a Na+/H+ exchanger on the luminal side of the bovine main pancreatic duct.
Marteau
C
C
INSERM U 260, Faculte de Médecine, Marseille, France.
Silviani
V
V
Ducroc
R
R
Crotte
C
C
Gerolami
A
A
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D066298:In Vitro Techniques; D009761:Nystatin / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010183:Pancreatic Ducts / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism*
D017923:Sodium-Hydrogen Exchangers; D009761:Nystatin; D010042:Ouabain; D000584:Amiloride; D012964:Sodium