AJP - Gastrointestinal and Liver Physiology, Vol 264, Issue 1 57-G63, Copyright © 1993 by American Physiological Society

ARTICLES

Preepithelial mucus-HCO-3 layer protects against intracellular acidosis in acid-exposed gastric mucosa

T. Kiviluoto, M. Ahonen, N. Back, O. Happola, H. Mustonen, H. Paimela and E. Kivilaakso
II Department of Surgery, Helsinki University Central Hospital, Finland.

The role of the preepithelial mucus-HCO-3 layer in protection against intracellular acidosis was investigated in isolated Necturus gastric antral mucosa exposed to luminal acid by simultaneous measurement of intracellular pH (pH(i)) and extracellular surface pH (pHs) in surface epithelium with microelectrode technique. Acidification of the luminal perfusate to pH 2.5 acidified pH(i) in surface epithelial cells from 7.33 +/- 0.02 to 7.20 +/- 0.04, whereas pHs fell from 6.75 +/- 0.21 to 5.20 +/- 0.25 (P < 0.01; n = 9), followed by a steady state for at least 2 h. Inhibition of epithelial HCO-3 secretion and transport by removal of serosal HCO-3 and CO2 (HEPES and O2 substitution) during acid exposure provoked a progressive acidification of pHs from 5.60 +/- 0.41 to 2.74 +/- 0.14 in 30 min (P < 0.01; n = 9), which was accompanied, after a 5- to 10-min delay, by acidification of pH(i) from 7.21 +/- 0.03 to 5.68 +/- 0.26 (P < 0.01). Digestion of the surface mucus gel by pepsin (5% wt/vol) at pH 2.5 caused a slow acidification of pHs from 5.22 +/- 0.59 to 3.60 +/- 0.46 within 2 h. This was followed by a more rapid acidification to 2.53 +/- 0.38 (P < 0.01; n = 7), with concomitant acidification of pH(i) from 7.19 +/- 0.05 to 6.03 +/- 0.33 (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				A. Allen and G. Flemstrom Gastroduodenal mucus bicarbonate barrier: protection against acid and pepsin Am J Physiol Cell Physiol, January 1, 2005; 288(1): C1 - C19. [Abstract] [Full Text] [PDF]

				O. Nylander-Koski, H. Mustonen, I. Vikholm, T. Kiviluoto, and E. Kivilaakso HCl causes less intracellular acidification in Necturus gastric mucosa surface epithelial cells than other acids Am J Physiol Gastrointest Liver Physiol, September 1, 2001; 281(3): G675 - G680. [Abstract] [Full Text] [PDF]

				G. Flemstrom and J. I. Isenberg Gastroduodenal Mucosal Alkaline Secretion and Mucosal Protection Physiology, February 1, 2001; 16(1): 23 - 28. [Abstract] [Full Text] [PDF]

				S. Abdulnour-Nakhoul, N. L. Nakhoul, and R. C. Orlando Lumen-to-surface pH gradients in opossum and rabbit esophagi: role of submucosal glands Am J Physiol Gastrointest Liver Physiol, January 1, 2000; 278(1): G113 - G120. [Abstract] [Full Text] [PDF]

				M. Phillipson, C. Atuma, J. Henriksnas, and L. Holm The importance of mucus layers and bicarbonate transport in preservation of gastric juxtamucosal pH Am J Physiol Gastrointest Liver Physiol, February 1, 2002; 282(2): G211 - G219. [Abstract] [Full Text] [PDF]