Abstract
Experiments performed on isolated intestinal segments from the marine teleost fish, the European flounder (Platichthys flesus), revealed that the intestinal epithelium is capable of secondary active HCO3- secretion in the order of 0.2-0.3 mu mol.cm(-2).h(-1) against an apparent electrochemical gradient. The HCO3- secretion occurs via anion exchange, is dependent on mucosal Cl-, results in very high mucosal HCO3- concentrations, and contributes significantly to Cl- and fluid absorption. This present study was conducted under in vivo-like conditions, with mucosal saline resembling intestinal fluids in vivo. These conditions result in a transepithelial potential of -16.2 mV (serosal side negative), which is very different from the -2.2 mV observed under symmetrical conditions. Under these conditions, we found a significant part of the HCO3- secretion is fueled by endogenous epithelial CO2 hydration mediated by carbonic anhydrase because acetazolamide (10(-4) M) was found to inhibit HCO3- secretion and removal of serosal CO2 was found not to influence HCO3- secretion. Reversal of the epithelial electrochemical gradient for Cl- (removal of serosal Cl-) and elevation of serosal HCO3- resulted in enhanced HCO3- secretion and enhanced Cl- and fluid absorption. Cl- absorption via an anion exchange system appears to partly drive fluid absorption across the intestine in the absence of net Na+ absorption
Original language | English |
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Pages (from-to) | R936 - R946 |
Journal | AMERICAN JOURNAL OF PHYSIOLOGY REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY |
Volume | 288 |
Issue number | 4 |
DOIs | |
Publication status | Published - Apr 2005 |