Localization of bicarbonate transport along the crypt-villus axis in rabbit ileum

Gastroenterology. 1994 Jun;106(6):1562-7. doi: 10.1016/0016-5085(94)90411-1.


Background/aims: HCO3- can be absorbed as well as secreted in the rabbit ileum. With 25 mmol/L HCO3- on the serosal side only, a serosa-to-mucosa flux (Jsm) is found; with 25 mmol/L on the mucosal side only, epinephrine elicits a mucosa-to-serosa flux (Jms). This study aimed to localize these two processes along the crypt-villus axis.

Methods: Excised ileal segments were exposed luminally to 2 mol/L Na2SO4 (hypertonic treatment) or to isotonic Ringer's solution for 15 minutes. Mucosa was then chamber-mounted, and measurements were made of Jsm or Jms and of short-circuit current (Isc) responses to glucose plus alanine and to either theophylline or epinephrine.

Results: With HCO3-/CO2 added to the serosal side only, hypertonically treated tissues showed a 22% decline in Jsm; a 25% decline in Isc response to theophylline; and a 71% decline in Isc response to glucose plus alanine compared with control. With HCO3-/CO2 added to the mucosal side only, tissues showed 92% and 87% declines in Jms and Isc responses to epinephrine, respectively, and a 87% decline in Isc response to glucose plus alanine. Histological examination showed destruction of villus caused by hypertonic treatment but sparing of crypt cells.

Conclusions: Both HCO3- and Cl- are secreted mainly by crypt cells and absorbed mainly by villus cells.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bicarbonates / metabolism*
  • Biological Transport / drug effects
  • Epinephrine / pharmacology
  • Hypertonic Solutions / pharmacology
  • Ileum / metabolism*
  • In Vitro Techniques
  • Microvilli / metabolism
  • Mucous Membrane / metabolism
  • Rabbits
  • Serous Membrane / metabolism
  • Theophylline / pharmacology
  • Tissue Distribution


  • Bicarbonates
  • Hypertonic Solutions
  • Theophylline
  • Epinephrine